Noise-canceling Headphones

The noise from a dental drill is one of the top reasons why many patients avoid the dentist. At LI Center for Healthier Dentistry, we embrace any new technology that makes our patient’s visits as comfortable as possible. That is why we have new active noise-cancelling headphones available during your treatment. Many patients plug the headphones into their smartphones or MP3 players and enjoy music during their dental procedures.

The very structure of noise-cancelling headphones creates a barrier that blocks high-frequency sound waves. They also add an extra level of noise reduction by actively erasing lower-frequency sound waves. How do they accomplish this? Noise-cancelling headphones create their own sound waves that mimic the incoming noise in every respect, except one: the headphone’s sound waves are one-hundred-and-eighty-degrees out of phase with the intruding waves.

If you look at the illustration below, you can see how this works. Notice that the two waves – the one coming from the noise-cancelling headphones and the one associated with the ambient noise – have the same amplitude and frequency, but their crest and troughs (compressions and rarefactions) are arranged so that the crests (compressions) of one wave line-up with the troughs (rarefactions) of the other wave, and vice-versa. In essence, the two waves cancel each other out, a phenomenon known as destructive interference. The result is that the listener can focus on the sounds he or she wants to hear.



Several components are required to achieve this effect:

Microphone - A microphone placed inside the ear cup "listens" to external sounds that cannot be blocked passively.

Noise-canceling circuitry - Electronics, also placed in the ear cup, sense the input from the microphone and generate a "fingerprint" of the noise, noting the frequency and amplitude of the incoming wave. They then create a new wave that is one-hundred-and-eighty-degrees out of phase with the waves associated with the noise.

Speaker - The "anti-sound" created by the noise-canceling circuitry is fed into the headphones' speakers along with the normal audio; the anti-sound erases the noise by destructive interference, but does not affect the desired sound waves in the normal audio.

Battery - The term "active" refers to the fact that energy must be added to the system to produce the noise-canceling effect. The source of that energy is a rechargeable battery.

Using these components, noise-canceling headphones are able to provide an additional reduction in noise of twenty decibels. That means about seventy-percent of ambient noise is effectively blocked.

Combined with our quieter electric dental drills, our noise-cancelling headphones provide a more comfortable and enjoyable dental experience.

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