How Do You Build a Wave Transmitter for Destructive Interference?

[a.glick]

How would I go about building a wave transmitter? Like in the noise cancelling headphones. I want to build a transmitter that absorbs sound waves, reflects them, and then shoots them out creating destructive interference.

 

[Bobbywhy]

a.glick, Welcome to Physics Forums!

You need to call things by their correct names! In all sciences, using the correct term is the only way to communicate ideas with accuracy.

1. Sound waves are emitted by a transmitter. Example: a speaker
2. Sound waves are received by a receiver. Example: a microphone
3. Audio can be amplified by an amplifier.
4. Sound waves humans can hear is known as "audio"


Noise cancelling headphones receive sound from the local environment. The electrical circuits inside amplify and invert that audio. That is, it is phase shifted 180 degrees. Then that audio is sent to the earphones of the person wearing the headphones. When those waves meet up with the incoming waves they should totally cancel out. This is known as destructive interference, as you said. The result expected is the wearer does not hear any sound from the external enviroment.

So, what you want to build is very similar to noise cancelling headphones, just as you said. You need to design and build a receiver, an inverting amplifier, and a speaker.

 

[a.glick]

so essentially i need to attach a microphone to a speaker. what am i supposed to use to create the phase shift of the wave?
thanks for your help bobbywhy.

 

[Bobbywhy]

a.glick, Visualize a simplified block diagram with 3 boxes:

1. Microphone
2. Inverting audio amp
3. Speaker

#1 feeds into #2 which feeds into #3.

Use the microphone to detect (receive) the sound you want to eliminate. Feed the output of the microphone into an inverting audio amplifier. Send the output of the amplifier to a speaker. Point the speaker towards the source of the sound. The inverted waves transmitted by the speaker will interfere destructively in midair with the sound waves you want to eliminate. Voila! Sound cancellation!

I suggest you consult with someone who can advise you and guide you through this process. It is not too difficult, but it seems to me you will need some help to make it work.

 

[PJC01]

Building a wave transmitter, similar to the technology used in noise cancelling headphones, would require a few key components and steps. First, you would need to have a source of sound waves, such as a speaker or microphone, which will produce the initial waves to be manipulated. Next, you would need a device or circuit that can absorb and reflect the sound waves, such as a noise cancelling chip or a phase inverter. This technology uses destructive interference to cancel out specific frequencies of sound, effectively reducing the overall noise level.

To create a wave transmitter, you would need to integrate this noise cancelling technology into a device that can emit the manipulated sound waves back into the environment. This could be achieved through the use of a speaker, which will amplify and project the reflected waves, or through a directional antenna, which can focus and direct the waves in a specific direction.

In order to fine-tune the transmitter and achieve the desired destructive interference, you may need to experiment with the placement and configuration of the components. This could involve adjusting the distance between the source of the sound waves and the noise cancelling device, or altering the settings on the noise cancelling chip.

Overall, building a wave transmitter that uses destructive interference to cancel out sound waves is a complex process that requires a solid understanding of sound waves and electronics. It may be helpful to consult with a professional or do further research on the specific technology used in noise cancelling headphones to ensure the best results.