Pure sine wave? - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 23rd June 2004, 11:53 PM   #1
diyAudio Member
 
Join Date: Feb 2002
Location: Western Sydney
Default Pure sine wave?

At http://headwize.com/projects/showfil...meier5_prj.htm
Jan Meier says this:
“Mechanical harmonic distortion in the inner ear: A pure 200 Hz sine wave not only makes the basillary membrane inside the ear vibrate at 200 Hz, but also at 400, 600, 800, 1000, 1200.... Hz. For sine waves between 200 and 3000 Hz these overtones have amplitudes of 33%, 13%, 6%, 4%, 2%, .... of the amplitude of the fundamental. Harmonic distortion in the inner-ear thus sums up to approximately 60%! Nonetheless, we only hear a pure sine-wave at the fundamental frequency since our brain has learned that this specific frequency spectrum belongs to a pure tone.”

This made me wonder if it was possible to create a waveform which would let us perceive only the fundamental, and if so what that waveform would look like?
Pete McK
  Reply With Quote
Old 23rd June 2004, 11:59 PM   #2
diyAudio Member
 
Join Date: Jan 2004
Location: Toronto, ON, Canada
Quote:
Nonetheless, we only hear a pure sine-wave at the fundamental frequency
Doesn't this mean that we ALREADY hear a fundamental frequency when one is played? The brain filters out the harmonics that the ear produces.
  Reply With Quote
Old 24th June 2004, 12:03 AM   #3
diyAudio Member
 
Join Date: Feb 2002
Location: Western Sydney
Default Ok...

then how about a waveform that would excite only the fundamental?
  Reply With Quote
Old 24th June 2004, 12:23 AM   #4
diyAudio Member
 
Paradise_Ice's Avatar
 
Join Date: Jun 2004
Location: cosmological consciousness
I think i know what your trying to say, but i dont have an answer,
an audiologist would have some kind of answer am sure, if it made sense is another thing, I really cant imagine what the wave would look like?
  Reply With Quote
Old 24th June 2004, 01:11 AM   #5
diyAudio Member
 
Join Date: Jan 2004
Location: Toronto, ON, Canada
Default Re: Ok...

Quote:
Originally posted by PeteMcK
then how about a waveform that would excite only the fundamental?
I'm thinking a waveform with harmonics of a negative amplitude (the pressure, anyway) might do it, but that's impossible.
  Reply With Quote
Old 24th June 2004, 01:41 AM   #6
diyAudio Member
 
Join Date: May 2004
Location: San Francisco
Send a message via AIM to joe carrow
Default Re: Re: Ok...

Quote:
Originally posted by 454Casull

I'm thinking a waveform with harmonics of a negative amplitude (the pressure, anyway) might do it, but that's impossible.
The lens in your eye projects an image on your retina that is upside down. Your brain corrects this and you never notice. Special glasses can flip it right side up (everything looks upside down)

I think you'd hear the missing harmonics like they're there. I don't think that this is something we need to worry about for HiFi, but it could be a consideration for cochlear implants or a future technology with direct connections to the brain!

-Joe

PS- I wrote more, but "check message length" tells me that this is over 10,000 characters!

EDIT: I completely misread the message that popped up. It was a little on the long side, and I thought that since I was new I might have some sort of introductory message length limit. What I was saying, though, is that with a wave "negative" would just mean "out of phase". So yes- I think that it's reasonably possible, if you studied an ear enough, to create a waveform that would produce a single fundamental at a given point. Of course, IIRC, the ear is a complicated thing and the part that converts motion to nerve impulses is not a single point.
  Reply With Quote
Old 24th June 2004, 02:25 AM   #7
diyAudio Member
 
Join Date: Apr 2004
Location: Costa Rica
Send a message via AIM to johninCR Send a message via MSN to johninCR Send a message via Yahoo to johninCR
You create the harmonic overtones and this makes you hear the fundamental without it being played. That's how several of the bass enhancement products like MaxxBass and others create the audio illusion of bass frequencies with drivers that won't play those low frequencies. The problem is that since those low frequencies aren't really played, you can't feel them so it doesn't sound quite real.
__________________
Everyone has a photographic memory. It's just that most are out of film.
  Reply With Quote
Old 24th June 2004, 09:58 AM   #8
diyAudio Member
 
mikee12345's Avatar
 
Join Date: Nov 2002
Location: NZ
Quote:
Originally posted by johninCR
You create the harmonic overtones and this makes you hear the fundamental without it being played. That's how several of the bass enhancement products like MaxxBass and others create the audio illusion of bass frequencies with drivers that won't play those low frequencies. The problem is that since those low frequencies aren't really played, you can't feel them so it doesn't sound quite real.


Certainly! perception and reality can be rather different things.
I downloaded a 'sub harmonic synthesiser' that adds 'lower bass'.Infact,all it does is make sinewaves more like square!
  Reply With Quote
Old 24th June 2004, 03:53 PM   #9
diyAudio Member
 
Join Date: Feb 2004
Location: US
Default too tricky

>then how about a waveform that would excite only the >fundamental?

That's a nice idea.

One has to think about the way sound excites the membrane of the ear. To greatly simplify things one can consider a string with fixed endpoints e.g. a guitar string. If you were able to deform the string in a perfect half wavelength shape then release it I believe you would have no harmonics. However, if you were to pluck it at a point you would get all sorts of travelling waves. Some of those travelling waves, however would superimpose on opposite travelling ones just right to cause standing waves i.e. resonance at various harmonics. These waves eventually die away due to internal losses e.g. friction.

So you could try two things: you could either try to stick somethings in your ear which only excites the 'fundamental' or you could try to supress the membrane from vibrating at harmonics. Perhaps this would be possible by playing tones at the harmonics which are '180 deg' out of phase with the 'fundamental', by this I mean that when the 'fundamental' is pressure maximum, the supression tone reaches pressure minimum. However this depends on exactly how sound pressure excites the tympanic membrane. You could have the opposite effect!

Once could easily do audio experiments to see if the brain filters this stuff out.
  Reply With Quote
Old 24th June 2004, 05:57 PM   #10
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally posted by mikee12345




Certainly! perception and reality can be rather different things.
I downloaded a 'sub harmonic synthesiser' that adds 'lower bass'.Infact,all it does is make sinewaves more like square!
Sinewaves that start to look like squares means that they have harmonics being added, specifically odd harmonics. If you add even harmonics the sine will start to look like traingle waves. Of course, for perfect square waves or triangles the harmonics need to have a specific level ratio to the carrier.

Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
SMPS to Pure Sine EUVL Power Supplies 2 11th June 2009 04:24 PM
Sine Wave Generator with bulbs (Sine-lightenment) Rodeodave Everything Else 6 21st July 2008 12:19 PM
Sine wave - Square & Triangle wave generator using Transistors / OP-Amps lineup Solid State 20 9th October 2006 12:15 AM


New To Site? Need Help?

All times are GMT. The time now is 10:05 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2