Active Noise Cancellation / Soundproofing

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In summary, the conversation discusses the viability of containing noise in a small area using active and passive noise cancellation technology, specifically in the context of headphone earpieces. The participants also consider the challenges posed by acoustics and the complexity of creating a system that can effectively cancel out noise from a specific source, such as a loud frog. Ultimately, it is determined that it is not possible to completely eliminate the noise within the headphone space, and any solution would need to be applied from the outside.
  • #1
jonnyb
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I would be very interested and grateful for guidance on how viable it would be to contain a noise in a relatively small area.
If the aim was to contain a noise through passive and active noise cancellation and the noise source could be contained within a small area, could the technology used in some on ear headphones be used to effectively contain/cancel a noise in a headphone ear piece?
So if a small speaker were to be placed under a headphone earpiece and a sound played ... would the noise cancelling technology in a typical set of headphones be able to help cancel that sound out within the headphone in which the small speaker is so that is not audible outside the headphone?
I am not as knowledgeable on this subject as I would like to be yet and so please forgive me.
I appreciate that the magnitude of the sound being played is relevant but it would be less than 10db.
Kind regards .. Jon
 
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  • #2
Electronics wise, it is piece of cake in the sense you mic the noise of the area and invert the signal and play it back out. You will need to do some phase adjustment in the circuit to compensate the mic and speaker characteristic. BUT the difficult part should be the acoustics. Sound can be directional and it has node and anti node depends on where you listen to it. That really get complicated. I worked on some active noise cancellation, but not have to deal with acoustics. You characterize the room, electronics is not bad. That's all I can offer as I don't know anything about acoustic other than set up my hi-fi system.

Ear phone don't have to deal with acoustic because the speaker is by your ears. The electronics should be easy. Your's is much harder. I suggest you look into Acura RL where they have active noise cancellation inside the cabin. Maybe look at some patents.
 
  • #3
Thanks for the quick reply. I think I need to create a different scenario. Let's say that the noise producer is not a small speaker but a small but quite loud frog that is sitting comfortably inside the speaker headphone which is pushed against a flat surface. (No frogs will be hurt or treated badly in this scenario!) I realized that I don't want to confuse things by having an example where the noise source was electrical and therefore could be part of the circuit. Can the existing active noise cancellation tech that is incorporated in a noise cancelling headphone be modified to help dampen the sound of the noisy frog to the world outside the headphone cup.
 
  • #4
I think elementing the frog's sound would not be possible because it would defy causality:

If the frog were to start talking, some time would transpire before the walls of the headphone experienced what he had done. Then, if they react, they are doing so to a noise that reached the listner already.

In the case where the frog is outside, his influence can be detected, placed through a signal processor that reacts to generate a signal, with the correct phase and magnitude, to essentially null Mr Frog's message.

The difficulty comes when you realize that the sensor, container, and speaker all have unique reactions to the various frequencies the frog can produce. Thus there is no easy solution to how you sample the noise and create an appropriate response. That's when you introduce a monitor on the listener's side, and a recursive algorithm continually varies aspects of the processing and judges success by how well it reduces the noise. So, Mr Frog may start out to be a nuisance to the untrained system, but it learns how to react over time.
 
  • #5
That's very interesting. So basically it's not possible to effectively cancel the noise of the frog within the headphone space before the noise reaches the listeners side.
The process would have to be applied from the outside and even then it certianly wouldn't be simple.
A shame .. In my ignorance I thought that the process could be applied within.
Thank you for your advice.
 

1. What is active noise cancellation?

Active noise cancellation is a technology used to reduce unwanted ambient noise by producing an opposite sound wave to cancel out the incoming noise. This is achieved through the use of microphones and speakers that work together to create a "negative" sound wave.

2. How does active noise cancellation work?

Active noise cancellation works by using microphones to detect incoming noise and then producing an inverted sound wave through the speakers. When these two sound waves meet, they cancel each other out, resulting in a reduction of overall noise.

3. What are the benefits of active noise cancellation?

The main benefit of active noise cancellation is that it can significantly reduce unwanted noise, making it easier to focus and concentrate in noisy environments. This can be especially useful for individuals who work in loud or busy settings, or for those who travel frequently.

4. Is active noise cancellation the same as soundproofing?

No, active noise cancellation and soundproofing are not the same. Soundproofing involves physically blocking or absorbing sound waves to prevent them from entering or leaving a space, while active noise cancellation uses technology to cancel out sound waves in a specific area.

5. Are there any limitations to active noise cancellation?

While active noise cancellation technology can be very effective, it does have some limitations. It works best for consistent, low-frequency noises such as airplane engine noise or background chatter, but may not be as effective for sudden or high-pitched noises. It also requires a power source to operate, so it may not be suitable for all environments.

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