Are urban environments "noisy" at ultrasound frequency ranges? If they are, does this cause problems for animals that can hear in these frequencies?

Submitted by derefr t3_ybsvrd in askscience

I recently purchased a soundbar, and I've noticed that my cat now doesn't want to enter the living room whenever the soundbar is on and receiving audio from any source — even if the soundbar itself is muted and so silent to my own hearing.

After eliminating other possibilities, I'm left with the hypothesis that my soundbar is producing some annoying or frightening noise in some ultrasonic frequency — a frequency that I can't hear, but my cat can. (I'd like to find out for sure, but ultrasound microphones are apparently expensive, and I'm not sure how to capture the audio coming from one.)

Do many electronic or mechanical devices produce incidental operational vibrations at ultrasonic frequencies? If we could hear these higher frequencies, would our constructed environments — cities especially — seem especially "noisy" in these frequencies? Are there any product standards or government regulations intended to limit ultrasonic "noise pollution"?

30

Comments

You must log in or register to comment.

AshPerdriau t1_itk1tup wrote

Ultrasonic animal deterrents are legally sold in many countries, including ones designed to deter human animals (the teenager-annoying ones). So yes, noise is a problem and that's how some people want it.

It's likely that your soundbar has a high frequency switching power supply, and entirely possible that it is emitting sound above your hearing (the upper limit decreases with age and can be under 10kHz). One cheap option is a frequency display app for your phone, which should go up to 20kHz or so. That won't give you "true" ultrasonic, but will cover some range that you probably can't hear, and may show harmonics of any actual ultrasound.

15

oddzod t1_itk2cbs wrote

As for a test, unplug it.

As to can they hear something you can't yup. Ignoring sounds that might or might not be comming out of the actual speakers, there is an effect called the piezoelectric effect. Ceramic capacitors are the worst for this. When they are physically flexed they induce a voltage across them. When a voltage is induced across them they flex. If the frequency is right it will make an auditable sound.

A lot of electronics use ceramic caps and are apply a frequency near the high end of human hearing. Most people can hear it. I'm one of the "lucky" ones that can. A lot of electronics emit a high pitch ringing noise that most people dont seem to hear, yet drive me nuts. Starting to question my sanity here.

12

Ch33kyMnk3y t1_itl5erw wrote

I know EXACTLY how you feel, see my post on this thread 🤣 we need a support group or something lol!

3

Nsikat t1_itkaxeo wrote

When I was up to my early 20's I could hear to about 22kHz (including some dog whistles). TV line whistle was a real pain. Now in my late 70's I can only catch 10kHz on a good day and often cut off around 8kHz.

9

BluesFan43 t1_itl7sys wrote

I have a lot experience with ultrasound for machinery monitoring. Can hear grease going into a bearing,

I can bear a tiny little relay in a multi ton transformer cabinet, it is on a card, on a motherboard, in a 1/8" thick seal cabinet with my gear.

I can hear your eyes open, your fingers running together, etc feom feet away. No real matter the noise levels from the thousands of horsepower of pumps running.

Can't pick up a voice.

Electronics can be noisy around 40 kHz.

A shovel moving gravel is noisy.

Keys rattle terribly.

When doing inspections outside, a bird walking by make a lot of noise

So yeah, cat's and dogs live in an entirely different noise level.

2

infrasoundjake t1_itlmrw2 wrote

The cheapest way I know to measure ultrasound is with this device. It makes normal .wav files, and you can check out the spectrograms in any audio editing software like Audacity (free). I don't think it's super well-calibrated, but it'll at least show you whether the ultrasound noise changes when you turn on the soundbar.

1

GeriatricZergling t1_itms5uq wrote

Somewhat related, my university has motion-activated light switches so the lights turn out if someone stops moving. Except in the labs and lab-animal housing, because apparently the motion sensor uses ultrasounds that's within the hearing range of mice, and they get stressed out by it.

1