Why can't a person hear ultrasound? Hammer people who hear what others don't hear

If you hear some sounds that other people cannot hear, this does not mean that you are having auditory hallucinations and it’s time to see a psychiatrist. Perhaps you belong to the category of so-called Hamers. The term comes from the English word hum, meaning hum, buzzing, buzzing.

Strange complaints

The phenomenon was first noticed in the 50s of the last century: people living in different parts of the planet complained that they constantly heard a certain uniform humming sound. Most often, residents of rural areas talked about this. They claimed that the strange sound intensifies at night (apparently because at this time the overall sound background decreases). Those who heard it often experienced side effects - headache, nausea, dizziness, nosebleeds and insomnia.

In 1970, 800 Britons complained about a mysterious noise. Similar episodes also occurred in New Mexico and Sydney.

In 2003, acoustics specialist Jeff Leventhal discovered that only 2% of all inhabitants of the Earth can hear strange sounds. Mostly these are people aged 55 to 70 years. In one case, a Hamer even committed suicide because he could not bear the incessant noise.

“It’s a kind of torture, sometimes you just want to scream,” this is how Katie Jacques from Leeds (Great Britain) described her feelings. - It's hard to sleep because I hear this pulsating sound continuously. You start tossing and turning and think about it even more.”

Where is the noise coming from?

Researchers have been trying to find the source of the noise for a long time. In the early 1990s, researchers at the Los Alamos National Laboratory at the University of New Mexico came to the conclusion that hummers hear sounds that accompany traffic and production processes in factories. But this version is controversial: after all, as mentioned above, most Hamers live in rural areas.

According to another version, there is actually no hum: it is an illusion generated by a diseased brain. Finally, the most interesting hypothesis is that some people have increased sensitivity to low-frequency electromagnetic radiation or seismic activity. That is, they hear the “hum of the Earth,” which most people do not pay attention to.

Paradoxes of hearing

The fact is that the average person is able to perceive sounds in the range from 16 hertz to 20 kilohertz, if sound vibrations are transmitted through the air. When sound is transmitted through the bones of the skull, the range increases to 220 kilohertz.

For example, the vibrations of the human voice can vary between 300-4000 hertz. We hear sounds above 20,000 hertz worse. And fluctuations below 60 hertz are perceived by us as vibrations. High frequencies are called ultrasound, low frequencies are called infrasound.

Not all people respond the same way to different sound frequencies. This depends on many individual factors: age, gender, heredity, the presence of hearing pathologies, etc. Thus, it is known that there are people capable of perceiving high-frequency sounds - up to 22 kilohertz and higher. At the same time, animals can sometimes hear acoustic vibrations in a range inaccessible to humans: bats use ultrasound for echolocation during flight, and whales and elephants presumably communicate with each other using infrasonic vibrations.

At the beginning of 2011, Israeli scientists found that in the human brain there are special groups of neurons that allow one to estimate the pitch of a sound down to 0.1 tones. Most animal species, with the exception of bats, do not have such “devices”. With age, due to changes in the inner ear, people begin to perceive high frequencies worse and develop sensorineural hearing loss.

Radioconstructor 2007 No. 2

Ultrasounds surround us everywhere; these can be the “negotiations” of animals, the noise of various equipment, as well as ultrasounds specially generated by echo sounders and medical devices. Unlike sounds in the audible range, ultrasounds affect us imperceptibly. And not always favorable. A clear example is that in a certain place, for example, near some equipment, you have a headache and your hearing is somehow impaired. All the symptoms of deafening, but there is silence all around. Apparent silence. “Decibels” of the ultrasonic range are pressing on your ears, they deafen you, but you cannot understand this, because you do not hear the acoustic vibrations interfering with you.

Using this simple device, you can not only determine the source of ultrasound and its intensity, but also “listen” to the ultrasound, determine the nature of its sound (intermittent, with changing frequency, etc.).

The basis of the device is the ultrasonic microphone MA40B8R (M1). The number “40” in its name indicates the frequency (40 kHz) at which it has maximum sensitivity. At frequencies below 32 kHz, sensitivity drops sharply (-90dB). This sensitivity characteristic makes it possible to use it for monitoring ultrasound without the use of special filters that suppress sound frequencies.

The ultrasonic level indicator circuit consists of a microphone M1, a two-stage amplifier on transistors VT1 and VT2 and an alternating voltage meter on diodes VD1, VD2 and a dial indicator MA. The alternating voltage from Ml is supplied to a two-stage amplifier through the sensitivity regulator R7. The amplified AC voltage is then detected by diodes VD1 and VD2. A constant voltage is generated at capacitor C6, proportional to the ultrasound volume level. This voltage is shown by the MA dial gauge.

To listen to ultrasound, a method is used to reduce its frequency to frequencies in the audio range by dividing it with a digital counter.

From collector VT2, an alternating voltage of ultrasonic frequency is supplied to the pulse shaper on transistor VT3. The transistor is turned on without bias at the base and opens like an avalanche when the amplitude of the alternating voltage at its base exceeds the opening barrier of the transistor.

Pulses from the VT3 collector are supplied to the counting input of the binary counter D1. The counter divides their frequency by 128. Then, from the output of the counter, pulses are sent to the headphones.

As a result, for example, ultrasound with a frequency of 40 kHz is reproduced by headphones as a sound with a frequency of 312.5 Hz (40/128 = 0.3125). Now we can “hear” ultrasounds, monitor changes in their frequency, and determine their intensity using a dial indicator. The disadvantage is that the sound volume in the headphones does not depend on the ultrasound volume, but this is compensated by the dial level indicator.

Most of the parts are installed on a printed circuit board made of fiberglass with one-sided foil. The board is placed in a plastic case and located along it. Next to it, in a hole specially cut into the body, there is an imported dial indicator (similar to the M470 indicator) with an end position of the scale. The total deflection current of the indicator needle is 300mA, and the resistance is 1200 Ohms. However, you can use any similar microammeter, with a scale of no more than 400mA and a resistance of at least 300 Ohms. Its sensitivity can be adjusted by connecting an additional resistor in series, the resistance of which will need to be selected experimentally.

The K561IE20 chip can be replaced with the K561IE16 counter. In this case, the output will be not the 4th, but the 6th pin of the microcircuit (you need to slightly change the printing of the board).

The power switch is a microswitch mounted by soldering onto the board. At the same time, the nut for fastening the toggle switch to the panel serves as an element for fastening the board in the case. Connector X1 is a socket for small-sized stereo headphones; it is also installed on the board. The connection diagram for this connector is such that the headphones operate in series.

The power source is a 9V Krona battery.

The adjusted resistor R7 can be replaced with a variable one, then it will be possible to adjust the sensitivity of the device within a wide range.

The printed circuit diagram of the board and the wiring diagram are shown in Figure 2, and Figure 3 shows how the device parts are placed in the housing.

Figure 2. Printed circuit board

Figure 3. Wiring diagram.

Figure 4. Layout diagram.

The amplification stages on transistors VT1 and VT2 need to be adjusted. Having set the adjusted resistor to the minimum sensitivity position (slider down all the way, according to the diagram), you need to measure the constant voltages on the collectors VT1 and VT2. If these voltages go beyond 2.5-3V, you need to select the resistance of the base resistors (R1 and R2, respectively).

To the question whether a person can hear ultrasound asked by the author Elena Guseva the best answer is everything is normal!
Different people hear different frequencies. Teenagers, for example, hear higher frequencies, but with age this gradually disappears.
By the way, modulated ultrasound is perfectly audible. This property is used to make bullshit to disperse demonstrators.

Answer from 22 answers[guru]

Hello! Here is a selection of topics with answers to your question: can a person hear ultrasound?

Answer from User deleted[guru]
Are you sure you’re not a mouse?)) Isn’t there anything about this in the instructions?

Answer from Mephistopheles - Orléans[guru]
Most likely, you heard a neighboring harmonic of a lower frequency

Answer from Ekaterina Chugunova[active]
No. the frequency is too high for the human ear. It is also impossible to hear infrasound - the frequency is too low. it's just a hoax

Answer from Valery Dyatlov[newbie]
The human ear can distinguish from 20 to 20,000 hertz (oscillation frequency), ultrasound cannot hear, now think that you have been beautifully deceived, but the paper endures.

Answer from User deleted[guru]
No two people are the same.
Some see near-infrared rays and ultraviolet, notice the flickering of incandescent light bulbs, some hear infrared and ultrasound.
Highest sensitivity in childhood.
In old age, in general, everything above 10 kHz is ultrasound (in the sense that it is no longer audible).
P.S. what's in the instructions? what frequency?

Answer from Valery Petrov[guru]
Could the sound be from the power supply? It happens

Answer from Ђgame@[guru]
At the low-frequency limit of the ultrasonic range, it still can. It is believed that ultrasonic waves occupy a frequency range from 20 kHz to 1 MHz.
So I also hear all sorts of retons and ultratones (ultrasonic washing machines).
And finally, the dog knows them, these manufacturers what frequency they set for their devices, maybe only 18 kHz. And this is not surprising to hear.
Maybe we really hear a harmonica, but we still hear))

Answer from Alexander[guru]
Ultrasound refers to electromagnetic vibrations with a frequency of 10,000-100,000 kHz. The human ear cannot hear such frequencies. And mice, as experience in operating such devices shows, simply don’t care about these sounds... But the seller makes money on nothing. And without any complaints... well, your mice are non-standard...
Although there is a scientifically proven way to get rid of rodents, using well-known BIOLOGICAL methods of control... CAT... or better yet, CAT. In a week he will simply catch all the mice in the house... He is a Hunter. He is on duty all 24 hours... This is his nature. Well, I’ve been convinced so many times of the correctness of this simple method...
Don't offend the cat... He is your friend... although he is marking his territory, he is a scoundrel...

Answer from Vsevolod Popov[guru]
the device was not developed and was not assembled in a store, the store is a point for accepting money and dispensing goods, but the developers - this is a more interesting topic, so that the device would scare away mice - it is actually set up on mice, that is, it is experimentally determined what frequency of sound affects annoying to mice or the frequency changes during operation
ultrasonic dog repeller - signal parameters 24.3 kHz, 116.5 dB
ultrasonic rodent repeller UZU-04 - frequency of sound vibrations: from 17-20 to 50-100 kHz
electronic cat - Sound frequency: - 30,000-70,000 Hz (automatically changes to prevent rodent adaptation)
Ultrasonic rodent repeller Tornado-400M operates in the frequency range from 18 to 70 kHz.
Ultrasonic device Grad A-500 is an innovative device with a unique pattern of sound vibrations that propagates high-frequency waves in a wide range: 4-64 kHz.
ultrasonic repeller of rodents, rats and mice LS – 927 frequency band 30,000 – 65,000 Hz
Acoustic vibration frequency of "Electrocat":
- when using the device in “Day” mode from 17-20 to 50-100 kHz;
- when operating the repeller in the “Night” mode from 5-8 to 30-40 kHz;
As a result, we have: 1 not all devices are audible to the human ear, 2 some people hear sound up to 20 kHz, 3 not all devices meet safety standards, 4 the store did not deceive you (I generally doubt that the seller has extensive knowledge about the effects of ultrasound on animals and person), 5 look at the signal frequency data (if any) of the device you purchased
Ultrasound is elastic sound vibrations of high frequency. The human ear perceives elastic waves propagating in the medium with a frequency of approximately 16-20 kHz; """Higher frequency vibrations are ultrasound""" (beyond the audible limit). Typically, the ultrasonic range is considered to be the frequency range from 20,000 to a billion Hz. Sound vibrations with a higher frequency are called hypersound
in theory it is called ultra because it is higher than the limit of audibility
just like ultraviolet - a person cannot see
just like infrasound - a person cannot hear
just like infrared radiation - a person cannot see
I wrote and wrote that I wrote that I didn’t understand))
The answer to your question will be - can a person hear ultrasound? -NO, that’s what ultrasound is for
It’s better to answer what device you have, make, model, manufacturer

These terrible sounds are all around us, but only a small group of people can hear them. They almost always come from cars - sometimes intentionally, sometimes accidentally. They are loud enough to cause irritation and headaches in people sensitive to them, although it seems that they are usually not loud enough to cause ongoing health problems. And scientists don't have a clear idea of ​​how common these sounds are or how harmful they are.

It is the result of more than a decade of research by Timothy Leighton, a professor of acoustics at the University of Southampton in England, in a class of sounds called "ultrasound." He spoke about his work at the 175th meeting of the Acoustical Society of America (ASA) on May 9.

Ultrasound is not very well defined, Layton said in an interview. In theory, he said, the sounds are too high-pitched for humans to hear. But in practice, these are sounds that are on the edge of hearing for infants, young adults, some adult women, and other groups with particularly acute hearing. And for them, ultrasound represents a growing problem that is not well studied or well understood, Layton said.

"A lot of people came to me and they said, 'I feel bad in some buildings,'" Layton said. “Nobody can hear it, I went to my doctor and got my hearing checked and everyone says it’s in my head.”

Part of the problem, Layton says, is that very few researchers are studying the problem.

"I think you'd be lucky to find even six people in the entire world working on this," Layton said. “And these, I think, are the reasons why many sufferers have turned up at my door.”

This does not mean that Layton's work is not part of the scientific mainstream; he was one of two co-chairs of the invited session on high-frequency sound at the ASA meeting and received the Royal Society's Clifford Paterson Medal for selected studies of underwater acoustics. But most acoustic researchers simply don't study high-frequency sound in human spaces; most acoustics experts said they had no knowledge to comment.

Sounds he didn't hear

Layton began his early work on ultrasound waves by going into buildings where people reported having symptoms. While he did not hear sounds, he recorded them using his microphones and constantly found ultrasonic frequencies.

"These are places where there might be 3 million or 4 million people a year," he said. “So it became clear to me that ultrasound is in public places where a minority will be affected, but in quantitative terms it is a large number of people.”

And the effects of ultrasound are not trivial.

“If you are in the ultrasound area and you are one of the sensitive people, you will experience headaches, nausea, tinnitus (ringing) and various other symptoms,” Layton said. “And once the exposure stops, you get better. In about an hour you’ll be fine.”

The response to ultrasound may seem like superstition, and researchers don't understand why this happens. But this is backed up by decades of consistent experimentation by a number of different researchers.

Layton is one of the few experts on the subject, and he doesn't know how many people are exposed to ultrasound or how serious the effects are.

The most famous event supposedly occurred when American diplomats in Cuba suffered a strange constellation of symptoms that officials initially attributed to some kind of ultrasound. The most severe symptoms of ultrasonic wave exposure include headaches, tinnitus and hearing loss, similar to those experienced by U.S. diplomats in Cuba. (Leighton, like most scientists, is skeptical that ultrasonic weapons were actually involved).

In reality, Layton said, the reason ultrasound is a problem is not because, in bizarre extreme cases, it can expose a tiny portion of the population to permanent hearing damage. More often, ultrasound is likely to expose a large, young, vulnerable portion of the population to discomfort and hearing irritation.

But why doesn't everyone hear these sounds?

Back in the late 1960s and early 70s, researchers first systematically studied what sounds could cause problems in the workplace, but were high enough that they would not become problematic in limited, low-volume doses. Based on these studies, governments around the world have come to a general guideline for workplace ultrasound: 20 kilohertz at medium volumes or 20,000 vibrations per second.

It's a very high-pitched sound - much higher than most adults hear. In the video below, the tone slowly rises from a low 20 hertz tone to 1000 times a 20 kilohertz tone. I don't hear anything once the tone goes up about 16 kilohertz. (But I can't say for sure that this is not a result of my headphones, but of my hearing.)

But this is not too important for all people. Almost everyone experiences hearing loss at the higher end of the spectrum as they age. And men, as a rule, lose hearing in these ranges earlier than women.

The problem with the 1970s studies, Layton said, is that they were conducted primarily on adult men, many of whom worked in noisy jobs and were likely to have fairly poor hearing. Governments around the world have ultrasound regulations governing these tests, Layton said. And these rules, designed for noisy workplaces, have come to dominate public spaces in developed countries, where people susceptible to ultrasonic waves may not be used.

"A grandma holding a baby could go into a public place where there's a lot of ultrasound exposure, and the baby will be agitated, and the grandma will have absolutely no idea what's going on."

There just aren't many researchers studying ambient ultrasound, Layton said, so data on where ultrasound is located is limited. So far, he said his crowdsourced experiments have only just managed to image ultrasonography in central London, but they have already provided some clues as to where ultrasound might be found.

Places ranging from train stations to sports stadiums to restaurants appeared to be unknowingly broadcasting ultrasound through certain door sensors or rodent control devices, Layton said.

Layton said there is no single culprit for ultrasonic waves. A number of machines create them completely unintentionally. Some speakers play them during test cycles. And Layton said he has found manufacturers of those devices who are interested in his research and fixing their ultrasound problems. Other industries, like manufacturers of devices designed to keep out pests from yards and basements, are more stubborn.

The next step for people who are concerned about ultrasound, Layton said, is to collect much more data.

Right now, ultrasound is difficult to research for the simple reason that most people can't hear them, so most people don't realize that it is a subject worth studying. It's difficult to do research into whether it poses any specific dangers, Layton said.

“We really can't test conventional ultrasound machines on young people and hurt them. I mean, it's just unethical,” he said. “And that’s alarming because you can go to a hardware store and for $50 you can buy a device that will affect your neighbor’s child. But at the same time, I will never be allowed to bring people into the laboratory and test the influence of ultrasound on them.”

But Leighton says interest is growing.

He recently issued a call for work on ultrasound and received about 30 messages, about 20 of which were worth publishing.

This interesting electronic project allows you to clearly hear a world of sounds beyond the limits of human perception. The ultrasonic microphone that you will create (Fig. 26.1) has a very wide range of domestic and technical applications: from detecting leaks of gases, liquids, mechanical wear of bearings, rotation mechanisms and reciprocating motion, for example, in cars, to detecting electrical leaks in insulators power lines. The entire world of sounds of living beings also becomes audible. Simple events - a cat walking on wet grass, the jingling of a key chain, even a plastic bag bursting - can be heard very clearly. On a warm summer night, a chorus of wonderful sounds can be heard as nature's orchestra of creatures ranging from bats to insects creates a cacophony of natural sounds beyond the range of the human ear, and the ultrasonic microphone makes inaudible sounds audible.

This handheld directional microphone easily detects and converts ultrasonic vibrations into sound. The addition of a parabolic reflector further enhances the capabilities of this device. Expect to spend between $30 and $50 on this cost-recovery device.

This project allows you to listen to the world of sounds, the existence of which few people know. The device is made in the form of a pistol, in the barrel of which there is an electronics unit. The rear panel contains switches and a volume control, a variable resistance trimmer and a headphone jack. The front of the device is a directional receiving transducer. The handle contains batteries.

The addition of a parabolic reflector option increases the directivity of the ultrasound source, providing ultra-high gain and greatly enhancing the device's long-distance sound reception capabilities.

Rice. 26.1. Ultrasonic microphone with parabolic reflector

Application of the device

One of the most interesting sources of ultrasonic mechanical vibrations are many species of insects that produce mating and warning signals. On a typical summer night, you can spend many hours listening to bats and other strange noises made by flora and fauna. A whole world of natural sounds awaits the user of the device. Many artificial sounds are also sources of ultrasonic vibrations and are recorded by the device. Below are a few examples, but these are just a few of the potential sources of ultrasound:

Gas leakage and air flow;

Water from spray bottles in case of leakage from the device;

Corona discharge, spark discharge or lightning generating devices;

Fires and chemical reactions;

Animals walking on wet grass and creating rustling sounds. This is a great tool for hunters and spotters, or just a way to find your pet at night;

Computer monitors, television receivers, high-frequency generators, mechanical bearings, strange sounds in cars, plastic bags, jingling coins.

The demonstration of this ultrasonic microphone also shows the use of the Doppler effect, where movement towards the source causes an increase in frequency, and movement away from the source causes a corresponding decrease in frequency.

The Doppler effect occurs when an observer moving towards a sound source perceives an increasing frequency. This is easy to imagine if you understand that sound travels in the form of a wave at a relatively constant speed. When an observer moves towards a sound source, he intercepts more waves in a shorter period of time, thus hearing a sound that appears to have a shorter wavelength or, correspondingly, a higher frequency. If it moves away from a sound source, a lower pitch frequency is heard compared to the frequency heard by a stationary observer.

To provide entertainment for both adults and children, you can hide a small test ultrasound generator and challenge your opponent to find it in the shortest possible time.

Basic diagram of the device

The microphone of the ultrasonic piezoelectric transducer TD1 perceives ultrasonic mechanical vibrations and converts them into an electrical signal due to the piezoelectric effect (Fig. 26.2). Coil L1 and the piezoelectric transducer's own capacitance form an equivalent resonant circuit at a resonance frequency of about 25 kHz. A resistor Rd is connected in parallel to the circuit. This parallel equivalent resonant circuit forms a high-impedance signal source, which is connected through capacitor C2 to the gate of field-effect transistor Q1. Resistor R1 and capacitor C1 decouple the drain bias voltage. Circuit design and shielding of input wires play an important role here, since this circuit is very sensitive to noise, feedback signals, etc.

The signal from the output of load resistor R2 of transistor Q1, through the isolation capacitor SZ and resistor R4, is fed to the input of amplifier I1A with a dimensionless gain equal to 50 and determined by the ratio of the resistances of resistors R6/R4.

Output I1A through capacitor C4 is connected via alternating current to mixer-amplifier I1B. The output of the I1C generator is connected to the circuit using a “special device” based on the CM mounting capacitor, created by a short wire from pin 8 of the IC1 element, which is twisted with a similar wire from pin 2 of the IV element (it is proposed to check the operation of the device without this device). The IIC generator produces signals of one of the frequencies, which is mixed with the received signals through the CM at the I1B input. The result will be a mixture of two signals, one of which represents the sum, and the other the difference of these signals, lying in the audio frequency range.

Capacitor C7 and resistor R17 form a bandpass filter that cuts out the sum of frequencies from the frequency mixture and passes the frequency difference at a level of 20 dB. Thus, the resulting low-frequency signal is the difference between the frequencies of the oscillator and the real signal. This is similar to the superheterodyne effect. The filter from C7 and R17 additionally decouples the signal

Rice. 26.2. Schematic diagram of an ultrasonic microphone

Note:

Proper placement of power wires will improve the noise performance of the circuit.

The wires to J1 should be short and as straight as possible.

Power wires must be connected from the back of the circuit board.

Rd is selected to dampen (calm down) the response of the converter. The expected value is 39 kOhm.

If possible, twist the wires into twisted pairs.

high frequency. The filtered signal represents the frequency difference, is rectified by diode D1 and integrated by capacitor C8. The rectified signal is in the audio range and can actually be heard. It is adjusted using a variable resistor R12 in the generator section and allows selective tuning to specific frequencies within the permissible range of the piezoelectric transducer TD1. The resulting audio frequency signals are supplied to the volume control R19 through the DC blocking capacitor SY. Capacitor C12 additionally filters out the remaining high-frequency signals. From the middle terminal of variable resistance R19, an audio signal is supplied to headphone amplifier 12 with an output impedance of 8 Ohms. The signal from output 12 is fed through capacitor C16 to the headphone jack J1. The power gain of 12 is small, and in addition to headphones, you can connect a low-power 8-ohm speaker to jack J1 for group listening. Filter R21/C4 further attenuates high frequencies.

Power supply 12 is isolated using resistor R20 and capacitor C15. This ensures circuit stability and prevents oscillations in the feedback loop and other unwanted effects.

The operating point of I1A, I1B, I1C is set to the average value of the supply voltage using a resistive divider R7/R11. Resistors R5, RIO, R15 compensate for the bias current.

Device assembly procedure

When assembling the device, first assemble the breadboard with hole punching, then the other sections of the device structure:

1. Arrange the components by ratings and purpose (separately resistors, capacitors, etc.) and check them with the specification (Table 26.1).

Table 26.1. Ultrasonic Microphone Specification

2. Insert the components starting from the left side of the perforated breadboard, following the layout shown in Figure. 26.3, to connect the board to other sections of the structures and using the 2 holes on the bottom right as guides. The board has dimensions of 5.72 × 5.72 × 0.25 cm. Instead, you can use a board with printed wiring of RSV conductors, which can also be purchased through the website www.amasingl.com. When making connections, use the component pins; connections between components are made on the back of the board (shown with a dotted line). On the component installation side there are connections shown as a solid line. It is recommended to try on larger parts before starting to solder their leads.

Always avoid jumpers made of bare wire, poor-quality solder joints, and possible short circuits due to soldering. Check the device circuit components for cold solder joints and poor solder joints.

Pay attention to the polarity of the capacitors, on the body of which the “+” sign indicates positive polarity, the other terminal of the polar capacitor will have, accordingly, negative polarity,

Rice. 26.3. Breadboard assembly

as well as the polarity of all semiconductor devices. The pinout of each microcircuit is determined by a key in the shape of a semicircle and the output of microcircuit 1 to the left of the key. The terminals of the variable resistances and socket J1 must physically match the holes for their installation in RP1.

3. Cut, strip and tin the wires to connect to J1 and solder them. These wires should be twisted and 5.08 cm long.

4. Make chassis CHAS1, front panel RP1, body EN1 and handle HAND1 as shown in Fig. 26.4.

Rice. 26.4. General view of the sections of the collection device structures, with the indicated dimensions for manufacturing

Rice. 26.5. Installing the breadboard on the chassis and external board connections

Note:

It is very important to ensure proper heat dissipation from the contacts of the TD1 converter before starting soldering. When in doubt, use nuts or slip-on connections to dissipate heat. Note that the short pin is internally connected to the converter body and to circuit ground. If there is no short circuit between this contact and the aluminum body of the converter, then this converter will be damaged as a result of overheating!

You can use a battery of 6 AAna9Vilina12V cells using 8 AA cells, which is placed in the HA1 handle. The 12V power supply allows you to increase the sound output of a low-power 8 Ohm speaker and its volume.

5. Prepare both ends of the shielded cable as follows. If the parabolic reflector option is used, you will need 45 cm of cable, if not, 15 cm (Fig. 26.5).

Rice. 26.6. The final design of the device using a reflector

Note:

The shielded cable is 45 cm long and passes through a small hole in the rear cover of the SARZ and the PARA12 reflector.

TD1 is placed in bushing BU1. This assembly is then inserted into the inside of a 13.2 cm long, 4.13 cm outer diameter cylindrical housing using O-rings. This placement of TD1 secures the transducer and protects it from shock.

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The converter connections are made in accordance with Fig. 26.5.

– carefully remove 1.9 cm of outer insulation, but so as not to damage the screen braid;

– cut through the screen braid with a sharp object, such as a pin, and twist the wire out of it. Gently tin only the ends to hold the strands together;

– carefully strip 0.64 cm of insulation from the central wire and tin it;

– check the finished cable for shorts or leaks using a multimeter in resistance measurement mode.

6. Solder coil L1, contacts of the piezoelectric transducer and damping resistor Rd to each other in parallel, as well as the ends of cable SH1 (central core to one common point, cable braid to another), see fig. 26.5. When soldering, be careful not to overheat the converter contacts or the center conductor insulation. If the contacts overheat, the component, especially the piezoelectric transducer, as discussed above, will fail. You can do a simple test on

Rice. 26.7. View of the assembled device design without using a reflector

short circuit between the metal body of the component and the shortest terminal. If the resistance is higher than 1 ohm, this means that you have damaged this part and it needs to be replaced. Mechanical connections using twisted harness, wire nuts, etc. shown above (see Fig. 26.5).

7. Assemble the device as shown. An assembly using a parabolic reflector is shown in Fig. 26.6, and in Fig. 26.7 – without it.

Preliminary electrical tests

To check the functionality of the system, follow these steps:

1. Turn off the device, connect the HS30 headphones, insert the 9V battery. Connect the multimeter in 100mA current mode to the contacts of switch R19 and quickly measure the current, which should be about 20mA. Turn off the multimeter and set the R19 regulator to the middle position. Notice the soft hissing sound in the headphones. Then turn on your computer or TV and configure the R19 to receive a clear tone from one of those audio sources. Turn off the sound source and gently rub two fingers together while listening to a clearly audible sound through the headphones. Check the entire range of the controller for unwanted feedback or false signals.

The device is now ready for final assembly. Pay attention to the test points and waveforms (see Figure 26.2). The shape and amplitude of the signals must correspond to those shown in Fig. 26.2.

2. Complete the final assembly by adding a PARA12 parabolic reflector to significantly increase the instrument's range (see Figure 26.6).

Please be aware that your device may sense strong magnetic fields because it is not shielded from them. Performing the Doppler effect test described above makes it easy to distinguish between these fields.

Special Note: Using a Standing Wave

It is possible to generate a standing wave in front of the TD1 piezoelectric transducer and improve the sensitivity of the system. Point the instrument at a stable, low-intensity ultrasonic energy source and carefully adjust the distance to the 2.54 x 2.54 cm metal plate mounted in front of the transducer face, observing the signal increase as it approaches the piezo transducer. This effect will occur in half-wave multipliers and is most pronounced near the converter. Use your own creativity to modify this simple action.

Additional notes regarding the use of the device

The device can provide many hours of fun for adults and children. For example, you can hide a small box with a 25 kHz frequency generator somewhere. The narrow radiation pattern of the device and its ability to register different signal levels will allow you to quickly detect this hidden source by the participants of the game, in turn, with jokes and jokes! Please note that the range of the device can exceed 400 m! This gives you a lot of options for choosing where to place your generator cache, and your imagination will tell you how to make it difficult to find. I have spent many enjoyable times with my children and friends using this equipment in play.

Recording the output signal

You can easily record the output signal using a recording device by connecting the auxiliary input to the headphone output jack. For simultaneous listening while recording, the “U” adapter can be used. With the adapter, you can use two sets of headphones with an output impedance of 8 ohms.