[bobopi]

Hi,

in the context of physiological recordings with small animals (guinea
pig) in a small anechoic chamber, I would like to use headphones as
speakers between, say, 100 Hz and 35 kHz. I'm interested in the
flattest response possible. I've selected a bunch of headphones, but
the shape of their frequency response is never given on their
constructors websites. Has someone performed tests ? I wonder, do they
have a flat response (more or less) or has their response been adapted
to the human ear ? Do you have some advice on some of these models ?
Here are the selected models:


*Beyer*

dt 770 pro
closed
5-35000Hz
http://www.beyerdynamic.de/en/broadc...eo-production/
products/headphonesheadsets/headphones.html?
tx_sbproductdatabase_pi1[showUid]
[showUID]=44&tx_sbproductdatabase_pi1[showUid]
[backPID]=93&cHash=cd6f9075a1

dt 880 pro
semi-open
5-35000
http://www.beyerdynamic.de/en/broadc...eo-production/
products/headphonesheadsets/headphones.html?
tx_sbproductdatabase_pi1[showUid]
[showUID]=1851&tx_sbproductdatabase_pi1[showUid]
[backPID]=93&cHash=cef9b324c4

dt 990 pro
open
5-35000 Hz
http://www.beyerdynamic.de/en/broadc...ctdatabase_pi1[showUid][showUID]=45&tx_sbproductdatabase_pi1[showUid][backPID]=93&cHash=cb51219012


*Fostex*

T50RP
semi-open
15-35000Hz
http://www.fostexinternational.com/docs/music_products/
rp_series_spec.shtml


*AKG*

K 702
open
10-39800Hz
http://www.akg.com/site/products/pow...id,1082,nodeid,
2,_language,EN.html
available in august

*Sony*

MDR 7509HD
closed
5-80000Hz
http://pro.sony.com/bbsc/ssr/product-MDR7509HD/


*Sennheiser*

HD 595/600/650
open
10-39000 Hz
http://www.sennheiser.com/sennheiser/icm_eng.nsf/root/09969


*Ultrasone*

Pro 750/2500
closed/open
8-35000Hz
http://www.ultrasone.com/index_en.php?
level=1&CatID=13.37&inhalt_id=45&shop_level=2&shop _CatID=1&shop_inhalt_id=0&do=showDetails&artikel_t yp=allgemein&artikel_id=17

I like this last one because it is magnetic shielded, which is
especially interesting when we perform intracerebral recordings which
are perturbated by magnetic fields but their S-logic system is not
that nice for my use I guess.

Thanks
Boris

[Ken[_8_]]

On Fri, 4 Jul 2008 04:19:08 -0700 (PDT), bobopi wrote:

Hi,

in the context of physiological recordings with small animals (guinea
pig) in a small anechoic chamber, I would like to use headphones as
speakers between, say, 100 Hz and 35 kHz. I'm interested in the
flattest response possible. I've selected a bunch of headphones, but
the shape of their frequency response is never given on their
constructors websites. Has someone performed tests ? I wonder, do they
have a flat response (more or less) or has their response been adapted
to the human ear ? Do you have some advice on some of these models ?


http://www.headphone.com/technical/p...ld-a-graph.php

[Angelo Campanella]

bobopi wrote:

Hi,

in the context of physiological recordings with small animals (guinea
pig) in a small anechoic chamber, I would like to use headphones as
speakers between, say, 100 Hz and 35 kHz. I'm interested in the
flattest response possible. I've selected a bunch of headphones, but
the shape of their frequency response is never given on their
constructors websites. Has someone performed tests ? I wonder, do they
have a flat response (more or less) or has their response been adapted
to the human ear ? Do you have some advice on some of these models ?
Here are the selected models:

Have you investigated small piezoelctric wafers? These are a slab of
for instance barium titanate or any of the the piezoectric families. The
output level is likely small at low frequencies.

Another posssibility is a condenser microphone driven as a transducer.
This will indeed be flat up to the resonance frequecy of the cavity
behind the diaphragm, about 20 to 30 kHz. A 1/4" microphone will be flat
up to your 40 kHz or higher, but the sound output SPL will be less.

What SPL levels do you need to conduct your work?

"Earphones" imply that you can allow the transducer to be near the ear..

Angelo Campanella

[Scott Dorsey]

bobopi wrote:
in the context of physiological recordings with small animals (guinea
pig) in a small anechoic chamber, I would like to use headphones as
speakers between, say, 100 Hz and 35 kHz. I'm interested in the
flattest response possible. I've selected a bunch of headphones, but
the shape of their frequency response is never given on their
constructors websites. Has someone performed tests ? I wonder, do they
have a flat response (more or less) or has their response been adapted
to the human ear ? Do you have some advice on some of these models ?
Here are the selected models:

The problem is that closed-back headphones use the ear canal as part of
a resonant system, and so the low end response varies depending on the
size and shape of your inner ear.

Note also that if you get above 20 KHz, the beaminess becomes a problem
even with headphones. Very small changes in position result in large
changes in response.

Consequently, your local audiologist can't test above 8 KHz. If you
want a full-range test, they put a pressure transducer in your ear
canal to act as a reference.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Kalman Rubinson]

On 4 Jul 2008 08:42:32 -0400, (Scott Dorsey) wrote:

The problem is that closed-back headphones use the ear canal as part of
a resonant system, and so the low end response varies depending on the
size and shape of your inner ear.

I ain't disputing your statements except that I think you are
referring to the external ear or external auditory meatus when you
talk about the ear canal. The middle and inner ears are internal.

Kal

[Ty Ford]

On Fri, 4 Jul 2008 07:19:08 -0400, bobopi wrote
(in article
):

Hi,

in the context of physiological recordings with small animals (guinea pig) in

a small anechoic chamber,

Please elaborate as to why you are doing this.

Regards,

Ty Ford


--Audio Equipment Reviews Audio Production Services
Acting and Voiceover Demos http://www.tyford.com
Guitar player?:http://www.youtube.com/watch?v=4RZJ9MptZmU

[bobopi]

On 4 juil, 16:19, Ty Ford wrote:
On Fri, 4 Jul 2008 07:19:08 -0400, bobopi wrote
(in article
):

Hi,

in the context of physiological recordings with small animals (guinea pig) in
a small anechoic chamber,

Please elaborate as to why you are doing this.

why or how ?
the idea is to be able to send various sound stimuli to a small animal
which is able to hear between, say 100-150 Hz and 35-40kHz. We use
intracerebral electrodes in order to investigate the properties of its
auditory cortex.

Our anechoic chamber is small, less than 1 cube meter. In a previous
post, I asked advice for a speaker with that frequency range. Then,
thanks to the replies, I realized than maybe headphones are better
suited insofar as the speaker has to be put very close to the ear, not
more than 5 centimeters.

Directivity might be a problem but we would try to put the speaker as
close as possible to the animal's ear (the animal is constrained).
Apparently, some professional headphones have the required frequency
range. I would use only one speaker of course and we would try to
shield the speaker given that magnetic fields may increase the noise
on our electrophysiological recordings.

We need a flat response of the speaker. Headphones might have kind of
"colored" sound output and be adapted to the human's ear. That is a
concern. Ultrasone headphones, for instance, are shielded, which
would help a lot, but has not a really flat response (at least the
Ultrasone HD 650) according to http://www.headphone.com/technical/
product-measurements/build-a-graph.php?
graphID[0]=255&graphID[1]=585&graphID[2]=417&graphID[3]=&graphType=0&buttonSelection=Compare
+Headphones

regards,

Boris

[Jens Rodrigo]

bobopi wrote:
in the context of physiological recordings with small animals (guinea
pig) in a small anechoic chamber, I would like to use headphones as
speakers between, say, 100 Hz and 35 kHz. I'm interested in the
flattest response possible. I've selected a bunch of headphones, but
the shape of their frequency response is never given on their
constructors websites. Has someone performed tests ? I wonder, do they
have a flat response (more or less) or has their response been adapted
to the human ear?


No headphone will show a linear frequency response, because their
response has been adapted to loudspeaker listening by average
human ears.

Cheers Jens

[answerman]

bobopi wrote in
:

Hi,

in the context of physiological recordings with small animals (guinea
pig) in a small anechoic chamber, I would like to use headphones as
speakers between, say, 100 Hz and 35 kHz. I'm interested in the
flattest response possible. I've selected a bunch of headphones, but
the shape of their frequency response is never given on their
constructors websites. Has someone performed tests ? I wonder, do they
have a flat response (more or less) or has their response been adapted
to the human ear ? Do you have some advice on some of these models ?
Here are the selected models:

snip....snip


Auditory researchers have been performing experiments on guniea pigs and
other small mammals for decades. You should be looking into the auditory
research literature to determine out what sound delivery systems
researchers have used in the past, what systems researchers are presently
using and how successful they have been in achieving the sort of
frequency response that you desire. At the very least, such a literature
review will give you a proper perspective on what is actually achievable
and on how realistic your requirements are.

There is only one system that has ever been developed that comes close to
achieving the frequency response specifications that you require, but it
is not something that you can buy off the shelf.

http://www.freepatentsonline.com/425...%2F4251686+OR+
4251686&stemming=on

http://patft.uspto.gov/netacgi/nph-P...HITOFF&p=1&u=%
2Fnetahtml%2FPTO%2Fsearch-bool.html&r=14&f=G&l=50&co1=AND&d=PTXT&s1=
4251686&OS=4251686&RS=4251686

[Boris Gourevitch]

answerman wrote:

snip....snip


Auditory researchers have been performing experiments on guniea pigs and
other small mammals for decades. You should be looking into the auditory
research literature to determine out what sound delivery systems
researchers have used in the past, what systems researchers are presently
using and how successful they have been in achieving the sort of
frequency response that you desire. At the very least, such a literature
review will give you a proper perspective on what is actually achievable
and on how realistic your requirements are.

as I posted before on another thread, I've already looked at that (Syka
et al., Wallace et al., Weinberger et al. etc...). Basically, to my
knowledge, there are mostly three cases:
- use of two way speakers, sometimes very far from the animal. Want to
avoid that given the room size. Moreover, flat frequency response is
almost unavoidable in this case.
- use of a microphone as a speaker (bruel and kjear 4134 in general).
Don't understand how it can work given the small size of the product.
Should likely be put into the ear but ear canal is somewhat small.
- use of headphones took into parts and shielded. We used to use that in
our lab but with a beyer dt 48 which is not very good in high
freauencies. I start to think that this is the best solution though,
using a headphone with a wider frequency range. However, I'm not sure
that we can put the headphone close enough to the animal's ear. The
farther the speaker, the less flat the frequency response.
Boris

[answerman]

Boris Gourevitch wrote in
:

answerman wrote:

snip....snip


Auditory researchers have been performing experiments on guniea pigs
and other small mammals for decades. You should be looking into the
auditory research literature to determine out what sound delivery
systems researchers have used in the past, what systems researchers
are presently using and how successful they have been in achieving
the sort of frequency response that you desire. At the very least,
such a literature review will give you a proper perspective on what
is actually achievable and on how realistic your requirements are.

as I posted before on another thread, I've already looked at that
(Syka et al., Wallace et al., Weinberger et al. etc...). Basically, to
my knowledge, there are mostly three cases:
- use of two way speakers, sometimes very far from the animal. Want to
avoid that given the room size. Moreover, flat frequency response is
almost unavoidable in this case.
- use of a microphone as a speaker (bruel and kjear 4134 in general).
Don't understand how it can work given the small size of the product.
Should likely be put into the ear but ear canal is somewhat small.
- use of headphones took into parts and shielded. We used to use that
in our lab but with a beyer dt 48 which is not very good in high
freauencies. I start to think that this is the best solution though,
using a headphone with a wider frequency range. However, I'm not sure
that we can put the headphone close enough to the animal's ear. The
farther the speaker, the less flat the frequency response.
Boris

None of the solutaions that you are considering are viable. Read the
patent reference I gave you, again. In the system described in that
patent, sound is produced by a push-pull electrostatic trasducer and is
coupled to the ear via a tube of appropriate diameter which can be at
least four inches long before you run into some impedance matching
problems.

[answerman[_2_]]

Angelo Campanella wrote in
:



bobopi wrote:

Hi,

in the context of physiological recordings with small animals (guinea
pig) in a small anechoic chamber, I would like to use headphones as
speakers between, say, 100 Hz and 35 kHz. I'm interested in the
flattest response possible. I've selected a bunch of headphones, but
the shape of their frequency response is never given on their
constructors websites. Has someone performed tests ? I wonder, do
they have a flat response (more or less) or has their response been
adapted to the human ear ? Do you have some advice on some of these
models ? Here are the selected models:

Have you investigated small piezoelctric wafers? These are a slab
of
for instance barium titanate or any of the the piezoectric families.
The output level is likely small at low frequencies.

Another posssibility is a condenser microphone driven as a
transducer.
This will indeed be flat up to the resonance frequecy of the cavity
behind the diaphragm, about 20 to 30 kHz. A 1/4" microphone will be
flat up to your 40 kHz or higher, but the sound output SPL will be
less.

What SPL levels do you need to conduct your work?

"Earphones" imply that you can allow the transducer to be near
the ear..

Angelo Campanella


There is no significant difference between using a piezo element
(bimorph) and a back-driven condenser microphone in this application.
Depending on the required SPL,a piezo bimorph might be a bit more linear
than a back-driven condenser microphone. On the other hand, for a given
diameter,the resonant frequency and upper frequency limit of a back-
driven condenser microphone is going to be much higher than that of a
piezo bimorph of the same diameter. In fact, the likelihood of using even
a 1/4" diameter piezo element (which will have very limited volume
displacement) to construct a sound delivery system that can provide a
flat response at the eardrum to 40KHz is zip to none. Additionally,
because both transducers are volume displacement sources, a closed,
sealed sound delivery system is required in order to achieve a flat
response down to 100Hz.

[Scott Dorsey]

In article ,
Kalman Rubinson wrote:
On 4 Jul 2008 08:42:32 -0400, (Scott Dorsey) wrote:

The problem is that closed-back headphones use the ear canal as part of
a resonant system, and so the low end response varies depending on the
size and shape of your inner ear.

I ain't disputing your statements except that I think you are
referring to the external ear or external auditory meatus when you
talk about the ear canal. The middle and inner ears are internal.

Yes, I mean the outer ear canal, the volume between the eardrum and the
outside world. The stuff on the other side of the eardrum is more
or less fixed volume (unless you get a bad cold).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."