Sound pressure patterns

[Bhootnike]

If you want to find the number of wavelengths in a pressure pattern :
e.g.

look at attachment


do you start counting from the compression ?
or from the rarefaction?
the answer is 2.5
but i dont get how so

[Lasercookie]

You can start from either. A wavelength is either from a compression to a compression or from a rarefaction to a rarefaction. Think of a sine wave perhaps. A wavelength there is from trough to trough or from a crest to a crest.



To be honest, the number of wavelengths seems like a a bit of an odd question (from looking at that segment you've given us, it looks like there's almost 3 full wavelengths, with the third being made from the bit of the left half and the bit on the right half). I'm not sure how that's useful information though.

It wasn't asking for the length of the wavelength was it?

[Bhootnike]

nah, it asked for number of wavelengths

thanks bro


btw

the principle of resonance is used by physicists to explain how didgeridoos create their notes:
which of the following best explains the principle of resonance as it applies to the didgeridoo

ans: wavelengths that are half integer wavelengths are reinforced by the cavity of the didgeridoos

What. ?