# Simplest Sensors for Education & My Hearing Studies

#### wahtsensor

Joined Sep 19, 2021
11
I am retired and have a hearing issue.

I found that if I do Valsalva (pressurize ears) my hearing improves considerably especially toward higher frequencies. I tested my hearing with an online tone generator adjusted so that 1000Hz is moderately loud. My hearing response normally goes only to about 4600Hz. If I do Valsalva I can then hear out to 7000 Hz and barely detect 7300Hz. I have asked the Dr and looked for details on Valsalva and hearing improvement, but did not find much. The inner ear is near the Carotid Artery, the Jugular Vein and the jaw hinge, why is Valsalva changing my hearing?

Warning - Valsalva causes stresses that may be harmful, so don't do Valsalva without understanding the issues.

My hearing is badly bothered when background music on TV interferes with speech. The spectrum analyzer shows why. My current speculation is that perhaps I am missing hearing certain octaves of voices on TV and that the background music is overwhelming some of the voice octaves that I can hear.

After years of not understanding my hearing and sound, these two simple instruments finally showed me a great deal of relevant information in about a week!

I just purchased a low cost oscilloscope and am very impressed by what it can do.

I'd like to learn more about my hearing and sounds. In addition, I would like to demonstrate sound, voice and musical instruments to my grandchildren. I just learned what octaves are and would like to show them.

In addition, I have a background in light research and would like sensors for the new oscilloscope. In addition, I don't understand using my computer as an oscilloscope and whether that should be an option for viewing sensors.

Any suggestions for the simplest low cost, flat, microphone type that would work with the oscilloscope. I want to show sound waveforms. If you think the computer approach is a good option as well, please mention.

Any suggestions
1) light sensor
2) video camera with manual control of gain
3) pressure sensor for measuring the pressure between the chest and upper arm
4) other sensors for educational purposes

Goal is to get started with low cost sensors that demonstrate waveforms in a reasonably representative and informative way.

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#### MrChips

Joined Oct 2, 2009
27,727
Welcome to AAC!

I am retired and have severe hearing loss in both ears. The loss in my right ear is very severe ( -80dB) and was diagnosed as a medical condition called schwannoma many years ago. This was treated with radiation therapy.

I have gone through three different sets of hearing technology, i.e. hearing aids for both ears. The current pair that I am wearing uses the latest digital technology and the results are absolutely amazing. I am a musician. I play piano, jazz guitar, classical guitar and electric bass. Before this current pair of hearing devices, my experience playing classical guitar was somewhat substandard. Now I have no complaints and for all intents and purposes my hearing is much improved and most of daily living is back to normal.

I am retired from university teaching. I have a lot of background in math, physics, and engineering. I have a lot of knowledge and experience in all things with electronics and computers. If you would like some assistance in your endeavors don't be afraid to ask.

#### wahtsensor

Joined Sep 19, 2021
11
I posted some details about my Valsalva experience on a forum at the Mayo Clinic.
https://connect.mayoclinic.org/discussion/hearing-loss_valsalva-improves_need-information/

My diagnosis was hearing loss due to nerve damage. If I did Valsalva, I might hear significantly better for a few seconds or less. That does not seem like nerve damage to me.

I don't understand the Valsalva issues, it might increase blood pressure in a way that is dangerous for some, so please don't do it without researching the risks.

Do you use an audio spectrum analyzer for your music?

Listen to TV and its background music. I think that I identify the piano keys that are often in TV background music. I expect or see octaves from strings, air tubes, voices and other things that vibrate by length.

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#### MrChips

Joined Oct 2, 2009
27,727
The recommended steps for medical diagnostic would be to get a referral by your primary health care provider for a hearing assessment at an audiology clinic. From there you would get another referral to a hearing specialist.

I do not use an audio spectrum analyzer for music. I understand the math and science behind spectral analysis. I can program a computer to compute the Fourier Transform. My MSc thesis was based on the application of the Fast Fourier Transform.

If you wish I can discuss with you the significance of octaves and harmonics as applied to music and musical instruments.

#### wahtsensor

Joined Sep 19, 2021
11
The recommended steps for medical diagnostic would be to get a referral by your primary health care provider for a hearing assessment at an audiology clinic. From there you would get another referral to a hearing specialist.

I do not use an audio spectrum analyzer for music. I understand the math and science behind spectral analysis. I can program a computer to compute the Fourier Transform. My MSc thesis was based on the application of the Fast Fourier Transform.

If you wish I can discuss with you the significance of octaves and harmonics as applied to music and musical instruments.
I contacted a Hopkins Specialist that had given me a hearing examination many years ago and asked for a referral for diagnosing my new tinnitus. He highly recommended a Dr, who I believe was a specialist, maybe on the inner ear. I got a cat scan to look for issues. Nothing showed up. There was no comment on the Valsalva.

I have just started to look at speech and background music on TV with my spectrum analyzer. Basically if it looks messy by eye in the spectrum analyzer, I can't understand the speech well. My wife says that the background music is loud but that she can understand it. My hearing goes out to 4600Hz and hers to about 10,500Hz.

I am now trying to interpret what I see in the spectrum analyzer as first priority. The many things seen in the spectrum analyzer are very interesting.

I don't have a background in music and it is difficult to describe the spectrum analyzer's display in words. With my voice high, I can created octaves, each octave with narrow frequency bandwidth. I can vary my voice where the frequency of each octave is getting lower for a short time and then comes back up in a second or so, looking like lines of saw teeth in the spectrum analyzer. Some of the musical instruments seem to create octaves but then there may be several different fundamental frequencies at once, other notes, and I don't see the clear and simple sequence of octaves that I see in my voice. I see a piano key as lasting a second or two, constant loudness, but often not showing octaves as my voice does. I assume that musical instruments can control the loudness of each octave? My current understanding of octaves is that the lowest frequency is the loudest and they are less loud for higher octaves. If that is not true please explain that. Harmony is?

If you would correct the usage of my sound terms and how things fit together, I'd appreciate it.

If I buy a hearing aid that amplifies the higher frequencies where I have looses, what would it do it for TV with its background music?

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#### MrChips

Joined Oct 2, 2009
27,727
I am going to try to make it as simple as possible.

What is an octave?

When we sing in western music we sing using the following notes:
do - re - me - fa - so - la - ti - do

There are seven notes and on the eight note we end on the same note that we started, but in a higher pitch.
The eight note is twice the frequency of the first note. This doubling of frequency is called an octave because it spans eight notes on the musical scale.

For example, if the first note is 1000Hz, the octave is 2000Hz. A note of a single frequency is a perfect sine wave. In other words, a perfect sine wave has only one frequency. On a spectrum analyzer, a single sine wave will appear as a single line on the frequency scale.

The human ear is very sensitive to frequency and changes in frequency. Our ear is a natural frequency analyzer.

There are few musical instruments that can produce a perfect sine wave. The only one I can think of is a flute. This is because a flute is a tuned air pipe. The pipe is a column of air that oscillates at one frequency. Hence it produces a pure tone when played softly.

All other instruments do not produce a single sine wave. They possess the tendency to produce multiple frequencies based on a single frequency for which it was intended to produce. This first frequency is called the fundamental or first harmonic. The additional frequencies are called overtones or harmonics. This mix of frequencies is what defines the quality and uniqueness of the sound produced by the instrument. This is called timbre. Every instrument has a unique timbre. Our ear is able to recognize the different timbre from different instruments even if they are playing the same musical note.

Harmonic content of two different musical instruments

The fundamental is also the 1st harmonic. The 2nd harmonic is double the frequency of the fundamental. The 3rd harmonic is three times the frequency of the fundamental, etc.

Piano

Horn

Thus, the sound produced by musical instruments and human voices is a complex mix of multiple frequencies, much more than simply fundamentals and octaves.

What is Harmony?

Harmony is different from harmonics. When multiple notes are sung or played together they may blend smoothly (in harmony) or unpleasantly to the ear (disharmony or dischord).

For example, when two notes, an octave apart, are played simultaneously, two cycles of the octave would blend perfectly with one cycle of the fundamental. They are in harmony.

From the same musical scale of notes, do and so blend perfectly. They harmonize well. This is because the frequency ratio of do and so is 2:3. Two cycles of do and three cycles of so fit in the same time frame. In music terminology, this called a perfect fifth because so is the 5th note in the musical scale.

As another example, the notes do, me and so harmonize well. This is called a triad chord consisting of the 1st, 3rd and 5th notes. When mixed together, the combined waveform might look like this:

Sound perception and discrimination in the human hearing

Lastly, the human ear itself is a frequency analyzer. It is able to detect different frequencies, overtones, harmonies and nuances in the acoustic pressure wave that reaches the ear drum. Of greater significance, when we process this information in the brain we are able to pick out single notes, voices, etc., that might be buried in a cacophony of multiple sounds and noise, for example, a specific ring tone of a smart phone in a noisy bar.

In summary, sound detection and discrimination is a very complex subject. It is much more than what one can observe using an audio spectrum analyzer.

A hearing device adds more than just sound amplification. Over the years, even before a baby is born, our ear and hearing has to learn the significance of different sounds. Our brain processes and interacts with sound in very complex ways. As we age and our hearing sensitivity diminishes, our perception of sound also changes. When one is fitted with a hearing device it will sound very unnatural at the start. One has to be prepared to retrain one's hearing and adapt to the new audio stimuli that one receives. Suddenly, the sound of rainfall, rustling of leaves, birds singing, water from a washroom faucet, and crunching a bag of potato chips will become a new experience that you have gradually forgotten.

#### Ya’akov

Joined Jan 27, 2019
6,859
A calibrated microphone is used with spectrum analyzers and similar gear to characterize rooms. This one: https://www.amazon.com/Dayton-Audio-EMM-6-Measurement-Microphone/dp/B002KI8X40 is a very inexpensive but apparently well liked option. You can download a response curve for the particular microphone you receive (by serial number) from their website. Note that it is very inexpensive and there are much more accurate options for much more money, though it is unlikely you would gain much by spending more.

Don’t forget that if you are doing audiology tests you also need headphones with a flat/known frequency response curve. Otherwise you will not be able to distinguish the frequency response of your ears from the transducer’s contribution.

If you are using an oscilloscope you might also have the ability to PLT plot FFTs (Fast Fourier Transforms, as mentioned by @MrChips).

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#### neonstrobe

Joined May 15, 2009
181
The sound produced by voices is a sequence of varying notes (at different pitches or "height") in a fairly rapid succession. A spectrum analyser generally needs several cycles of a fixed frequency to be able to recognise it. You could consider purchasing an audio sound card for your computer which has an analysis capability. I don't know of any particular ones to recommend but I am sure some on here could. To "see" a voice you need to plug a microphone into such a sound card and sample the sound at a rate faster than the highest frequency which is expected (by at least a factor of 2). You can then display the sound signal and perhaps obtain a Fourier transform which will indicate whether there are particular harmonics. However, the point is that spoken voices are changing all the time, and you won't be able to regenerate a voice sound from a spectral response, only from the recorded sampling.
I can see what you are trying to do, but it will be something you will need to get in depth to achieve good results. FOr example, while harmonics which are even multiples of a fundamental tone "harmonise" as it were, so that thirds (5th semitone up) and fifths (seventh semitone up) blend in, instruments to not actually produce exact harmonics. Their different timbres arise from the harmonics being very slightly off the mathematical niceties.

#### wahtsensor

Joined Sep 19, 2021
11
I am going to try to make it as simple as possible.

What is an octave?

When we sing in western music we sing using the following notes:
do - re - me - fa - so - la - ti - do

There are seven notes and on the eight note we end on the same note that we started, but in a higher pitch.
The eight note is twice the frequency of the first note. This doubling of frequency is called an octave because it spans eight notes on the musical scale.

For example, if the first note is 1000Hz, the octave is 2000Hz. A note of a single frequency is a perfect sine wave. In other words, a perfect sine wave has only one frequency. On a spectrum analyzer, a single sine wave will appear as a single line on the frequency scale.

View attachment 248378

The human ear is very sensitive to frequency and changes in frequency. Our ear is a natural frequency analyzer.

There are few musical instruments that can produce a perfect sine wave. The only one I can think of is a flute. This is because a flute is a tuned air pipe. The pipe is a column of air that oscillates at one frequency. Hence it produces a pure tone when played softly.

All other instruments do not produce a single sine wave. They possess the tendency to produce multiple frequencies based on a single frequency for which it was intended to produce. This first frequency is called the fundamental or first harmonic. The additional frequencies are called overtones or harmonics. This mix of frequencies is what defines the quality and uniqueness of the sound produced by the instrument. This is called timbre. Every instrument has a unique timbre. Our ear is able to recognize the different timbre from different instruments even if they are playing the same musical note.

Harmonic content of two different musical instruments

The fundamental is also the 1st harmonic. The 2nd harmonic is double the frequency of the fundamental. The 3rd harmonic is three times the frequency of the fundamental, etc.

Piano
View attachment 248380

Horn

View attachment 248379

Thus, the sound produced by musical instruments and human voices is a complex mix of multiple frequencies, much more than simply fundamentals and octaves.

What is Harmony?

Harmony is different from harmonics. When multiple notes are sung or played together they may blend smoothly (in harmony) or unpleasantly to the ear (disharmony or dischord).

For example, when two notes, an octave apart, are played simultaneously, two cycles of the octave would blend perfectly with one cycle of the fundamental. They are in harmony.

View attachment 248390

From the same musical scale of notes, do and so blend perfectly. They harmonize well. This is because the frequency ratio of do and so is 2:3. Two cycles of do and three cycles of so fit in the same time frame. In music terminology, this called a perfect fifth because so is the 5th note in the musical scale.

As another example, the notes do, me and so harmonize well. This is called a triad chord consisting of the 1st, 3rd and 5th notes. When mixed together, the combined waveform might look like this:

View attachment 248397

Sound perception and discrimination in the human hearing

Lastly, the human ear itself is a frequency analyzer. It is able to detect different frequencies, overtones, harmonies and nuances in the acoustic pressure wave that reaches the ear drum. Of greater significance, when we process this information in the brain we are able to pick out single notes, voices, etc., that might be buried in a cacophony of multiple sounds and noise, for example, a specific ring tone of a smart phone in a noisy bar.

In summary, sound detection and discrimination is a very complex subject. It is much more than what one can observe using an audio spectrum analyzer.

A hearing device adds more than just sound amplification. Over the years, even before a baby is born, our ear and hearing has to learn the significance of different sounds. Our brain processes and interacts with sound in very complex ways. As we age and our hearing sensitivity diminishes, our perception of sound also changes. When one is fitted with a hearing device it will sound very unnatural at the start. One has to be prepared to retrain one's hearing and adapt to the new audio stimuli that one receives. Suddenly, the sound of rainfall, rustling of leaves, birds singing, water from a washroom faucet, and crunching a bag of potato chips will become a new experience that you have gradually forgotten.
Thanks for the very clear and thorough explanation. I'm studying.

#### wahtsensor

Joined Sep 19, 2021
11
A calibrated microphone is used with spectrum analyzers and similar gear to characterize rooms. This one: https://www.amazon.com/Dayton-Audio-EMM-6-Measurement-Microphone/dp/B002KI8X40 is a very inexpensive but apparently well liked option. You can download a response curve for the particular microphone you receive (by serial number) from their website. Note that it is very inexpensive and there are much more accurate options for much more money, though it is unlikely you would gain much by spending more.

Don’t forget that if you are doing audiology tests you also need headphones with a flat/known frequency response curve. Otherwise you will not be able to distinguish the frequency response of your ears from the transducer’s contribution.

If you are using an oscilloscope you might also have the ability to PLT plot FFTs (Fast Fourier Transforms, as mentioned by @MrChips).
The microphone looks perfect, thanks.

I am looking at pre-amps. Is the 48 vdc supply always included but sometimes not mentioned, always assumed present?

I have done an uncalibrated hearing test based on an online tone generator. It produces single frequencies. It instructs to go to 1000Hz and set the loudness control to moderately loud. After that setting at 1000Hz, it warns not to use the loudness control to increase loudness to increase hearing. This avoids loud sounds at frequencies where hearing is down. I assume that a medical hearing test involves a similar process where the loudness at each frequency is increased - always limited to safe levels - until the patient detects the sound. ? Then the test ends?

The tone generator drives my laptop speakers. For my tests, the normal TV volume would have usually been louder.

I read that loud high frequencies can be more damaging to parts of the ear. Since my hearing normally ends around 4600Hz, dropping quickly, and if I do Valsalva it goes to 7000Hz or 7300Hz, I avoid or minimize using the higher frequencies from the online tone generator.

I also view the tone generator on the spectrum analyzer. The spectrum analyzer uses my smartphone microphone. At first look, it appears to have a broad and flat response. I realize that everything is uncalibrated.

The spectrum analyzer seems in a way like a metal detector, it shows many interesting sounds. I had a somewhat broad and persistent sound at around 59Hz. I didn't hear anything. I had been trying to identify it and was checking AC power sources. Finally last night, I started going through the house. It got stronger at the refrigerator, 15 feet away behind a wall. When I put the mic into the opening at the side of the refrigerator, the spectrum analyzer signal turned white. The next time the 59Hz signal was lost the refrigerator was off. Next, if I place my finger over the mic opening, a broad low frequency signal appears. Is that a sound or artifact? Sound from blood flow in my finger? When I look at the sounds coming from TV, I wonder why it is such a cluttered mess with loud annoying music, jumpy music being broadcast.

Google Play's Spectriod works great on my smartphone, free.

"I have the Octave RTA on my iPhone and iPad. The bigger screen of the iPad makes it more useful."
https://onyx3.com/SpectrumAnalyzer/

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#### wahtsensor

Joined Sep 19, 2021
11
What I really need right now is a few posters with smartphone spectrum analyzers identifying a few of the wonderland of sounds that I'm seeing while hearing............

#### Audioguru again

Joined Oct 21, 2019
5,435
I learned to "pop my ears" with an action with the back of my tongue in my throat years ago. It must be similar to Valsalva to balance air pressures in the inner ear tubes.
In my late 50ies I noticed that TVs and radios sounded muffled (loss of high audio frequencies) because I thought they "hid the microphone" making the sounds muffled. Then I had difficulties with conversations.

I was a senior and hearing tests for seniors are free so 6 years ago I got a test that showed normal-for-my-age high frequency hearing loss (a surprise to me) and got demo hearing aids to try. I could not stand it and quickly returned them. Friends told me that they should have been turned up only a little at first so I went to another hearing place and they performed the test with the same results. Their demo hearing aids were properly turned up only a little at first then a little more after one week and again at two weeks then turned up to the maximum I need after 3 weeks and they are excellent. They have noise suppression and compression of sounds that are too loud when not set to the Music mode and do other useful tricks. My government helped me pay for them.

I could have easily made huge hearing aids with no features and carry around the circuit and battery in a box. My new tiny hearing aids sit on the top of my ears and can barely be seen with a little wire feeding signals to the tiny speakers in my ear canals. Inexpensive tiny batteries last for 10 days, new hearing aids have rechargeable batteries.
Hearing aids that are entirely in the ear canals cannot produce enough sound level without feedback squealing.
Each year I am given a free hearing test and any adjustments. In 6 years the hearing aids have been turned up a little, twice.

Here is a graph of normal hearing loss vs age:

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#### wahtsensor

Joined Sep 19, 2021
11
@Audioguru again

You were very similar to my situation. I was told that it was nerve damage.

But then there is the Valsalva. To give an example, I have a mailbox alarm. Hanna. In the last two years, I could hardly hear when it went off. I do Valsalva when I notice it and the sound goes from hardly audible to loud.

Valsalva causes pressure changes that I do not understand. This Mayo Clinic picture and comments on Tinnitus shows that the Carotid Artery, Jugular Vein and jaw hinge are very close to the Cochlea.
https://www.mayoclinic.org/diseases-conditions/tinnitus/multimedia/tinnitus/img-20007277

(I wish I knew how to copy and paste that picture in the post. 'Copy image address' does not work.)

The thought has occurred - do some people as they age have pressure on their ears, from blood or other, that affects their high frequency hearing? In one second of experiment, I can have my hearing go from failing at >4600Hz to failing at >7000Hz. I believe that frequency range is extremely important for comprehending speech. I am also concerned about the hearing aid approach of increasing the volume of the higher frequencies in my ear. That sounds very loud in my ear. Is that OK?

I looked for a year and got nowhere until I found the online tone generator and could observe the exact frequencies where Valsalva extended my hearing. It is very significant. I can't understand why pressurizing my ear area would extend my hearing so significantly. Is it simply that Valsalva moved a blood vessel off my Cochlea?

I realize that I'm an old guy headed for a hearing aid, but this is interesting.......

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#### Audioguru again

Joined Oct 21, 2019
5,435
I understand that high frequency hearing loss and tinnitus are caused by the hair cells in the inner ear (that resonate at their own frequencies) become worn out or broken by loud sounds or old age. Without my hearing aids I cannot hear anything beep like my oven or smoke detector. The old hair cell remains in my inner ears produce phantom very high frequency continuous tinnitus that is always there but not loud and I simply ignor it. When I was young I heard the tinnitus high frequencies whenever I strained doing exercises like done by Valsava.

Cheap hearing aids are being sold lately that say you adjust them yourself without using an expensive doctor or audiologist. That is ridiculous. A hearing deficiency is a medical problem which is why my government health system helps pay for them.

#### MrChips

Joined Oct 2, 2009
27,727
I am not a hearing specialist. I make the following assumptions and observations:

1) The purpose of the hearing aid is to overcome the deficiencies in your hearing. It would be foolhardy to attempt to do this yourself.

2) Ambient noise in any situation remains the same. What has changed is your perception of the noise as your hearing level has gradually changed over the years. When fitted with a new hearing device you have to retrain your brain to adapt to the new stimuli. This will take time but you will adapt in time.

3) Talk to a hearing specialist who understands your situation and observations.

4) As the previous member said, a proper hearing aid is not cheap. My hearing aids cost over \$2000 each. I wear hearing aids in both ears continuously while I am awake. My hearing loss is severe, -80dB above 1000Hz in the right ear.

-20dB = 1/10 gain
-40dB = 1/100
-60dB = 1/1000
-80dB = 1/10000

Power is the square of the voltage.
Hence the power reduction at -80dB is 1/100000000.

Without hearing aids I am practically deaf in one ear, and can hardly hear in the other. With hearing aids my life is almost normal in most respects. Hearing the sound of raindrops on the car roof while driving is annoying but a well appreciated new experience.

#### Audioguru again

Joined Oct 21, 2019
5,435
My hearing aids have noise reduction and compression of loud sounds when they are set to Automatic mode. In Music mode those features are turned off.