# Sound frequency

#### Evilinside

I'm currently studying vibrations and frequencies. I know that humans can hear from a range of 20Hz-20kHz. I was wondering if sound energy could reach a frequency where it was no longer really sound. Is this possible?

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#### dextercioby

Homework Helper
Sound waves are simply molecular vibrations which propagate with a certain velocity and have frequencies in the range 20 Hz-->20KHz.The essential defining part is the frequency.I don't see the relevence of energy (proportional to the sq.of the wave amplitude) in this matter.

Daniel.

#### amt

As the waves get into higher and higher frequencies, they are not auditble anymore. however they can get visible, when the frequency reaches that of light.

#### izzie

amt said:
As the waves get into higher and higher frequencies, they are not auditble anymore. however they can get visible, when the frequency reaches that of light.
aka the electromagnetic spectrum - - also, what you said is really only true in low level physics :rofl:

#### Integral

Staff Emeritus
Gold Member
Do not confuse mechanical sound waves with electromagnetic waves they are very different animals. Yes sound waves exist above the range we can hear. For examples, a dog whistle, since dogs and many other animals can hear much higher frequencies then men (or women) they respond to the whistle while we hear nothing. Even more important then that is the entire field of ultrasonics. Jewelers use ultra sonics in baths to clean rings, your digital camera uses ultra sonics to focus. There are lots of other applications for, and examples of, ultrasonic devices.

#### lord_jebus

im doing an experiment on ultrasonics. i have to find out where ther's a hole in a block of aluminium. what should i expect to see on the oscilloscope and how can i measure the size of the hole from my data? it says on another site there should be impedence i.e a disturbance but im not really noticing much. also can anyone give me formulas for percentage error accuracy error and random error in calculations

#### dimensionless

I know that in at least some substances, acoustical waves can only propagate when they are below a certain frequency.

#### Vinek

As the waves get into higher and higher frequencies, they are not auditble anymore. however they can get visible, when the frequency reaches that of light.
i want to ask you about this quote how couls you say "however they can get visible, when the frequency reaches that of light" i beleve it but can you give me some prof about it be i have to reply to some one

my email :- oum_ganeshansh1@yahoo.co.in

#### cjameshuff

i want to ask you about this quote how couls you say "however they can get visible, when the frequency reaches that of light" i beleve it but can you give me some prof about it be i have to reply to some one
There is no proof because it's not true. As Integral said, EM waves are very different from sound waves. Long wave radio goes down as far as 148.5 kHz, interference from power lines at 60 and 50 Hz is common, and ELF radio communications in the tens of Hz were used with submarines. Ultrasound easily goes through the kHz range into the MHz, and in some cases into the GHz or even THz range. Sound waves and EM waves can easily be created with identical frequencies, but they will still clearly be different phenomena.

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