The Naked Scientists

The Naked Scientists Forum

Author Topic: What makes a sound louder than another sound?  (Read 12552 times)

Offline EvilHomer15

  • Jr. Member
  • **
  • Posts: 10
    • View Profile
What makes a sound louder than another sound?
« on: 01/03/2011 04:06:49 »
The question is pretty much in the topic title.

This is something I have been wondering about for a little while now

What makes us hear some sounds louder than other sounds?
For example - what happens when you turn up the volume on your TV - how come our brain can analyze the wave signals to be louder than a lower volume?


 

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5339
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
What makes a sound louder than another sound?
« Reply #1 on: 03/03/2011 04:09:31 »
Sound is a compression wave, rather like squeezing a molecular-sized accordion; this compression or longitudinal wave propagates through air. A louder sound is one with the same frequency but a bigger amplitude. In other words, the amount that the wave is moving the air backwards and forwards is greater, which means that it moves your ear drum more when it enters the external auditory canal. Your ear perceives a louder sound to be one that provokes a bigger displacement of the eardrum; hence a more energetic wave is a louder wave.

Chris
 

Offline EvilHomer15

  • Jr. Member
  • **
  • Posts: 10
    • View Profile
What makes a sound louder than another sound?
« Reply #2 on: 03/03/2011 07:27:51 »
Thank you for your much appreciated response.
 

Offline RD

  • Neilep Level Member
  • ******
  • Posts: 8132
  • Thanked: 53 times
    • View Profile
What makes a sound louder than another sound?
« Reply #3 on: 03/03/2011 14:04:34 »
There are a couple of human complications

1. human perception of loudness is frequency dependent


http://en.wikipedia.org/wiki/Equal-loudness_contour

So two sounds can be of equal intensity but one will be perceived as louder because it has a different frequency, (a different pitch).


2. Stapedius reflex

The ear has a variable sensitivity control, analogous to variable pupil diameter in the eye, called the stapedius reflex. It reduces the sound energy reaching your inner ear when sound (within a certain frequency band) is above a threshold. So an engine in a quiet environment sounds loud when it starts, then fraction of second later your stapedius reflex kicks in and makes it sound quieter, but the actual engine noise is unchanged. 
    

http://www.thenakedscientists.com/forum/index.php?topic=14909.msg177234#msg177234
« Last Edit: 03/03/2011 14:26:53 by RD »
 

The Naked Scientists Forum

What makes a sound louder than another sound?
« Reply #3 on: 03/03/2011 14:04:34 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums