Adaptive hearing protection device

Thread Starter

jagruti mahajan

Joined Jul 20, 2018
21
I want to design adaptive hearing protection device. A protection device which stops unwanted noise if noise levels are high, but allows sound to enter the ear when noise levels are low.
For that I need some electronic circuitry. Do any any suggestions for this.
The flow will be like Microphone then controller (Electronic circuit) and then actuator to open or close the gap of device.
 

ebeowulf17

Joined Aug 12, 2014
3,059
I want to design adaptive hearing protection device. A protection device which stops unwanted noise if noise levels are high, but allows sound to enter the ear when noise levels are low.
For that I need some electronic circuitry. Do any any suggestions for this.
The flow will be like Microphone then controller (Electronic circuit) and then actuator to open or close the gap of device.
Do you want the actuator output to be a simple on/off control, or should it be a linear, proportional output, opening and closing the gap to varying degrees?

Do you have the mechanical side of this figured out yet? Are you picturing a servo, a stepper motor, a solenoid, something else?
 

Thread Starter

jagruti mahajan

Joined Jul 20, 2018
21
Do you want the actuator output to be a simple on/off control, or should it be a linear, proportional output, opening and closing the gap to varying degrees?

Do you have the mechanical side of this figured out yet? Are you picturing a servo, a stepper motor, a solenoid, something else?
I am thinking to use piezo actuators which when you apply some voltage, deformed.
Mainly it must be like if noise outside is greater the gap must be closed (you will not listen anything)
and if noise outside is less or normal , the gap must be open (normal speech , alarms ).
For workers who are in production dept with loud noise but if they go to cafeteria , they can communicate with others without removing hearing protection device.
To promote the use of hearing protection, the hearing protection is made to fit as comfortable as possible, allowing the user to wear the protection all day.
 

Reloadron

Joined Jan 15, 2015
4,919
I am active in the shooting sports and when shooting I wear a pair of these. The idea being I can carry on normal conversation but any surrounding loud sounds like gun shots are clipped in the internal amplifier.
  • Sleek, extremely low profile earcup design allows for full clearance of firearm stock
  • Automatic 4 hour shut-off increases battery life
  • AUX jack connects to MP3 players and scanners
  • Automatically shuts off loud impulse noise to a safe 82dB while amplifying conversation and range commands
  • Convenient folding design for easy storage
  • One single power and volume control knob
  • Air Flow Control™ technology
  • Black leatherette headband with sporty hunter green earcups
  • Water resistant
OK, I see you want as small as a hearing aid device rather than a bulky earmuff design. Something like what I mentioned but small hearing aid size. I would start with a basic hearing aid and include circuitry to clip the loud sharp sounds. Any sound exceeding a preset db level is clipped. That is how I would approach it and the person wearing the device would need two, one for each ear. The tiny amplifier technology is already there, you are only adding a clipping to that.

Ron
 

ebeowulf17

Joined Aug 12, 2014
3,059
I am active in the shooting sports and when shooting I wear a pair of these. The idea being I can carry on normal conversation but any surrounding loud sounds like gun shots are clipped in the internal amplifier.
  • Sleek, extremely low profile earcup design allows for full clearance of firearm stock
  • Automatic 4 hour shut-off increases battery life
  • AUX jack connects to MP3 players and scanners
  • Automatically shuts off loud impulse noise to a safe 82dB while amplifying conversation and range commands
  • Convenient folding design for easy storage
  • One single power and volume control knob
  • Air Flow Control™ technology
  • Black leatherette headband with sporty hunter green earcups
  • Water resistant
OK, I see you want as small as a hearing aid device rather than a bulky earmuff design. Something like what I mentioned but small hearing aid size. I would start with a basic hearing aid and include circuitry to clip the loud sharp sounds. Any sound exceeding a preset db level is clipped. That is how I would approach it and the person wearing the device would need two, one for each ear. The tiny amplifier technology is already there, you are only adding a clipping to that.

Ron
Most (maybe all) modern hearing aids have compression for moderately loud sounds and clipping for dangerously loud sounds already. A modern hearing aid that is well fitted is the solution... although they're prohibitively expensive!

There are also more moderately priced devices that aren't legally defined as hearing aids - although it's not at all clear to me what makes them different, other than the fact that "real" hearing aids are regulated and have much greater safety assurances. Here's one example:
https://www.etymotic.com/consumer/personal-sound-amplifiers/bean-qsa.html

If the TS wants something as small as a hearing aid, I can't imagine how actuators physically opening and closing ports will possibly fit in the ear canal - and even if they did, I imagine battery life would be horrible. I think something like hearing aid or shooting muffs would be the better approach.

That said, there's a downside to all of these devices. As an audio engineer and someone with moderate-to-severe hearing loss, trust me on this:
Anything that interferes with the normal sound path, where sounds coming from different directions bounce off the pinnae (outer ear folds,) will greatly hamper people's ability to determine the directions sounds are coming from, and you discriminate background noise from the sound they want to focus on. There are incredibly complicated comb filtering phase cancellation effects which happen when sounds enter the ear naturally from different angles, and our brains process that information to better identify and locate sounds.

Giving up that ability is a worthwhile tradeoff on a loud factory floor, but no-one is going to willingly wear them in a crowded cafeteria because, where people with ok hearing can easily focus on who they want to hear on a crowded room with their natural ears, they won't be able to pick one voice out from all the others in a busy environment. I think it will be very difficult to get people to wear these things all day!
 

Reloadron

Joined Jan 15, 2015
4,919
Most (maybe all) modern hearing aids have compression for moderately loud sounds and clipping for dangerously loud sounds already. A modern hearing aid that is well fitted is the solution... although they're prohibitively expensive!

There are also more moderately priced devices that aren't legally defined as hearing aids - although it's not at all clear to me what makes them different, other than the fact that "real" hearing aids are regulated and have much greater safety assurances. Here's one example:
https://www.etymotic.com/consumer/personal-sound-amplifiers/bean-qsa.html

If the TS wants something as small as a hearing aid, I can't imagine how actuators physically opening and closing ports will possibly fit in the ear canal - and even if they did, I imagine battery life would be horrible. I think something like hearing aid or shooting muffs would be the better approach.

That said, there's a downside to all of these devices. As an audio engineer and someone with moderate-to-severe hearing loss, trust me on this:
Anything that interferes with the normal sound path, where sounds coming from different directions bounce off the pinnae (outer ear folds,) will greatly hamper people's ability to determine the directions sounds are coming from, and you discriminate background noise from the sound they want to focus on. There are incredibly complicated comb filtering phase cancellation effects which happen when sounds enter the ear naturally from different angles, and our brains process that information to better identify and locate sounds.

Giving up that ability is a worthwhile tradeoff on a loud factory floor, but no-one is going to willingly wear them in a crowded cafeteria because, where people with ok hearing can easily focus on who they want to hear on a crowded room with their natural ears, they won't be able to pick one voice out from all the others in a busy environment. I think it will be very difficult to get people to wear these things all day!
Wow thanks for sharing all of that. I also wasn't quite getting the actuators part as to making things fit and be fast enough?

Thanks
Ron
 

DickCappels

Joined Aug 21, 2008
6,101
You can do that with a semi-passive circuit utilizing a tungsten filament thermistor.
https://patents.google.com/patent/US8699720?oq=walter+chu

I wrote the provisional patent application for that one and I can put you in touch with the only company on that can make the tungsten thermistors (or you can buy the first 10,000 of them from me :) .

We found that headphone companies are not interested in this sort of thing because there is no market for it.
 

KJ6EAD

Joined Apr 30, 2011
1,570
I wrote the provisional patent application for that one and I can put you in touch with the only company on [Earth] that can make the tungsten thermistors (or you can buy the first 10,000 of them from me :) .
I love it when someone has such perfect knowledge of or connection to a topic. It makes me smile. :cool: I suspect the T.S. is dismayed that there is so much prior art and realizes what they want to do is no easy or quick project. :(
 

ebeowulf17

Joined Aug 12, 2014
3,059
You can do that with a semi-passive circuit utilizing a tungsten filament thermistor.
https://patents.google.com/patent/US8699720?oq=walter+chu

I wrote the provisional patent application for that one and I can put you in touch with the only company on that can make the tungsten thermistors (or you can buy the first 10,000 of them from me :) .

We found that headphone companies are not interested in this sort of thing because there is no market for it.
That's really cool!

There are passive, volume limited headphones on the market - did they steal your idea, or are they using some other method?
http://www.us.jvc.com/headphones/kids/ha_kd6/
 

DickCappels

Joined Aug 21, 2008
6,101
That's really cool!

There are passive, volume limited headphones on the market - did they steal your idea, or are they using some other method?
http://www.us.jvc.com/headphones/kids/ha_kd6/
It is not my idea, it was the invention of one Walter Chu in Hong Kong.

No way to tell without taking it apart. The low price suggests some simple means of limiting sound pressure level. Some of them use simple diode clippers, which is about as cheap as you can get.
 

ebeowulf17

Joined Aug 12, 2014
3,059
It is not my idea, it was the invention of one Walter Chu in Hong Kong.

No way to tell without taking it apart. The low price suggests some simple means of limiting sound pressure level. Some of them use simple diode clippers, which is about as cheap as you can get.
That makes sense. Diode clipping is cheap and easy, and probably considered "good enough" for the protected volume children's market.

I did notice the patent made a point of saying this novel method was distortion free... which diode clipping would definitely not be!
 

WBahn

Joined Mar 31, 2012
25,115
I still use by dad's sonic earplugs when I shoot that are now about 70 years old and they still work great. Purely mechanical and I can carry on a normal conversation but even the heaviest reports from the firearms is reduced to a quite comfortable level.

What is it that you are trying to do that is not already available on the market?
 

DickCappels

Joined Aug 21, 2008
6,101
The thermistor-based limiter sounds very good, but if it is modifying the envelope to limit the volume that is a kind of distortion. You probably would not call it harmonic distortion except at frequencies below the low frequency cutoff of the thermistor.

The diode clippers induce harmonic distortion which is said (not by me) to damaging to hearing at high frequencies.
 

KJ6EAD

Joined Apr 30, 2011
1,570
They mentioned two techniques, clipping and compression. The manufacturers understandably don't publish their schematics to protect their intellectual property from thieves. Both techniques can be implemented in various ways, the latest being software controlled digital signal processing (DSP). Literature is available from open sources for older methods of automatic gain control (AGC).
 
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