Register to reply

What makes two sounds similar?

Share this thread:
Feb12-12, 01:50 PM
P: 38
i have been wondering this for a long time...

for example:
if we say the word "hello" with a loud pitch scientifically speaking higher amplitude
if we say the word "hello" with a low amplitude
if we say "hello" really fast
if we say "hello" very slow
if we say "hello" normally

the question:
what make all the above sounds similar?? as in if we graph the above sounds what would remain constant in all the graph??

thank you
Phys.Org News Partner Physics news on
New complex oxides could advance memory devices
Nature's designs inspire research into new light-based technologies
UCI team is first to capture motion of single molecule in real time
Feb12-12, 03:15 PM
P: 5,632
Wikipedia has this to say:

Propagation of sound

The behavior of sound propagation is generally affected by three things:
A relationship between density and pressure. This relationship, affected by temperature, determines the speed of sound within the medium.
The propagation is also affected by the motion of the medium itself. For example, sound moving through wind. Independent of the motion of sound through the medium, if the medium is moving, the sound is further transported.
The viscosity of the medium also affects the motion of sound waves. It determines the rate at which sound is attenuated. For many media, such as air or water, attenuation due to viscosity is negligible.

But the thing that REALLY makes them similar is that all sound is a longitudinal wave....
the above referenced articles discusses this....Light, in contrast, is transverse.
Feb12-12, 03:26 PM
Sci Advisor
HW Helper
tiny-tim's Avatar
P: 26,148
hello anj16!
Quote Quote by anj16 View Post
if we graph the above sounds what would remain constant in all the graph??
the shape
it'll always be the same, except it may be higher or lower on the page, or stretched or squeezed horizontally and/or vertically

Feb12-12, 09:10 PM
PF Gold
P: 1,909
What makes two sounds similar?

anj16, Welcome to Physics Forums! It is important that we all use terms accepted by science to describe experiments. Otherwise, folks will be confused as to our meaning and miss the point. For example, the term "amplitude" is quite different from the term "pitch".
As for your question in the OP, there are similiarities in those examples you gave. They are described by "acoustic signature". Just Google that and see the Wikipedia page plus references. In classifying and identifying particular ships and submarines and also in identifying specific species of birds and frogs we use an "acoustic fingerprint". Google that, too.
Feb12-12, 09:26 PM
DaveC426913's Avatar
P: 15,319
pitch (frequency)
amplitude (loudness)
tone/envelope (shape)
harmonics (multiple sounds)

For all your sounds, the first two can vary, but it is the third - the tone - that makes them all sound similar.

Alternately, you could keep the pitch and amplitude the same and change the tone, to get sounds that are very different.

Say the word 'woah' very slow, 'w' then 'o' then 'ah'. The major difference between the three is the tone of the sound.

Tone is the shape of each individual peak/valley. There are sine waves, sawtooth, square waves etc. The wider the shape (within the cycle), the more round the tone (like 'o'). The thinner the shape, the thinner the sound (like 'w').

See here. There's a little audio clip on the right.

There are other factors, such as harmonics, that play into the 'sound' of sound.
Feb13-12, 02:15 AM
Borek's Avatar
P: 23,723
If you wonder what makes them all be understood the same way - that is, why we hear "hello" each time, and not some other random word - check Liberman-Mattingly motor theory of speech perception (and related theories).
Feb13-12, 04:52 AM
P: 38
Thank you all for helping me out

just to clarify DaveC426913 would i be consistent with your explanation if i say that the number of peak and valleys remain constant making the sounds sound similar???

Register to reply

Related Discussions
A is similar to B is equivalent to A^k is similar to B^k? Calculus & Beyond Homework 5
Linear Algebra- prove that A is similar to B then A inverse is similar to B invese. Calculus & Beyond Homework 15
About SOUNDS Introductory Physics Homework 2
How do you describe sounds in words? General Discussion 9
Which sounds better? General Discussion 8