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:
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_typ=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.
> 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 ?
> 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..
bobopi <bo...@pi314.net> 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."
On 4 Jul 2008 08:42:32 -0400, klu...@panix.com (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.
On 4 juil, 16:19, Ty Ford <tyreef...@comcast.net> wrote:
> On Fri, 4 Jul 2008 07:19:08 -0400, bobopi wrote > (in article > <8bc6dca1-68e9-40cf-b76a-7525ceea8...@m3g2000hsc.googlegroups.com>):
> > 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&button Selection=Compare +Headphones>
bobopi <bo...@pi314.net> 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.
> 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.
> 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
>> 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.
