At which frequency does "ear canal gain" start for headphones?
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 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
 14th July 2004, 10:49 PM #1 454Casull   diyAudio Member   Join Date: Jan 2004 Location: Toronto, ON, Canada At which frequency does "ear canal gain" start for headphones? Assuming a typical circumaural headphone, when would the 12dB/octave gain start?
Svante
diyAudio Member

Join Date: Feb 2004
Location: Stockholm
Re: At which frequency does "ear canal gain" start for headphones?

Quote:
 Originally posted by 454Casull Assuming a typical circumaural headphone, when would the 12dB/octave gain start?
I'm not really an expert on this, but I could possibly make an educated guess. I would suggest that it would occur at the same frequency as any "room gain", just that the "room" is pretty much smaller. If the diameter of the cavity is some 4 cm, half a wavelength would fit into that at some 4 kHz. That would be a rough guesstimate. Hmm, this means that headphones should be compensated for this. Maybe they are, I don't know.

Edit: But wait, you call it "ear canal gain" in the subject line. The ear canal would have nothing to do with what I described. The ear canal acts like a pipe resonator, also around those frequencies. That resonance is responsible for the increased sensitivity of the ear in the range 1-5 kHz.
__________________
Simulate loudspeakers: Basta!
Simulate the baffle step: The Edge

454Casull
diyAudio Member

Join Date: Jan 2004
Re: Re: At which frequency does "ear canal gain" start for headphones?

Quote:
 Originally posted by Svante I'm not really an expert on this, but I could possibly make an educated guess. I would suggest that it would occur at the same frequency as any "room gain", just that the "room" is pretty much smaller. If the diameter of the cavity is some 4 cm, half a wavelength would fit into that at some 4 kHz. That would be a rough guesstimate. Hmm, this means that headphones should be compensated for this. Maybe they are, I don't know. Edit: But wait, you call it "ear canal gain" in the subject line. The ear canal would have nothing to do with what I described. The ear canal acts like a pipe resonator, also around those frequencies. That resonance is responsible for the increased sensitivity of the ear in the range 1-5 kHz.
I thought the gain started at the frequency whose wavelength was longer than 1/2 the longest dimension of the volume of the listening enclosure. Wouldn't the length of the ear canal be the longest dimension?

 15th July 2004, 12:46 AM #4 Svante   diyAudio Member     Join Date: Feb 2004 Location: Stockholm 454: Again, with little practical experience from this: I think that this 1/2-wavelength-of-the-biggest-dimension rule is appropriate for box shaped rooms. With headphones, we have h cavity outside the head, and then the earcanal. This is not a box-shaped room, so I guess that that rule does not nessecarily hold. OTOH the resonance in the earcanal is maybe 3kHz, so the number turns out about the same. Why are you asking in the first place? __________________ Simulate loudspeakers: Basta! Simulate the baffle step: The Edge
 15th July 2004, 12:51 AM #5 454Casull   diyAudio Member   Join Date: Jan 2004 Location: Toronto, ON, Canada I was just curious. Actually, the question stemmed from my wondering how much excursion a headphone driver would have to undergo to produce the entire audible spectrum.
 15th July 2004, 03:46 AM #6 BillFitzmaurice   Banned   Join Date: May 2004 Location: New Hampshire There's no such thing in an ear, any more than there is in a car. In small spaces pure air pressure achieved via compression of the air within the space is the medium by which frequencies are transmitted. This, by the way, is the origin of the term SPL- Sound Pressure Level.
Svante
diyAudio Member

Join Date: Feb 2004
Location: Stockholm
Quote:
 Originally posted by BillFitzmaurice There's no such thing in an ear, any more than there is in a car. In small spaces pure air pressure achieved via compression of the air within the space is the medium by which frequencies are transmitted.
The main question here is "when is the space small?". It is certainly small for low frequencies, but for high frequencies (eg 20 kHz) it is definitely large. Somewhere in between those frequencies the "room gain" starts. This frequency would be roughly 4 kHz for the headphones, roughly 100 Hz for a normal living room.

"A tweeter is big, and a woofer is small, acoustically."
__________________
Simulate loudspeakers: Basta!
Simulate the baffle step: The Edge

Svante
diyAudio Member

Join Date: Feb 2004
Location: Stockholm
Quote:
 Originally posted by 454Casull I was just curious. Actually, the question stemmed from my wondering how much excursion a headphone driver would have to undergo to produce the entire audible spectrum.
Ok, so the pressure inside a small cavity is the volume flow multiplied by the acoustic impedance of the cavity. In absolute terms:

p=U*1/(wC)

Since the velocity (v) is the derivative of displacement (x), and flow (U) is the velocity multiplied with the surface (S) of the membrane:

p=wxS/(wC)=xS/C

C is the acoustic compliance

C=V/(rho0*c^2)

so p=xS*rho0*c^2/V, or

x=pV/(S*rho0*c^2)

Assuming the p=1 Pa (94 dB), V=10e-6 m3 (10 ml), S=0.0005 m2 (5 cm2), rho0=1.2kg/m3 and c=345 m/s, the displacement would be 0.14 um. (I Hope I got it right...)
__________________
Simulate loudspeakers: Basta!
Simulate the baffle step: The Edge

 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 Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post danielwritesbac Chip Amps 20 30th November 2008 01:27 AM KCHANG Full Range 55 1st December 2006 09:21 AM joho Pass Labs 26 22nd December 2005 03:47 PM OA51 Chip Amps 21 8th March 2005 10:16 AM Circlotron Digital Source 3 19th May 2004 03:15 PM

 New To Site? Need Help?

All times are GMT. The time now is 06:10 AM.