Re: [AUDITORY] Tweeters for noise trauma

[Bob Masta <audio@xxxxxxxxxxx>]

Speaker specs are always given at 1 meter distance.  Animals being exposed are
usually much closer.

Note that this can cause its own problems if you are trying to expose multiple
animals using multiple close-by speakers, which will create interference
patterns.  With noise stimuli, I have been able to reduce that problem somewhat
by using two unrelated noise sources to drive alternate tweeters in the array.

Another issue is that the animal will move around in its cage, and may thus
move out of the main beam of a close-by speaker if it has space to do so.

Since you mentioned mice, I expect you will be working above 20 kHz.  Tweeter
frequency responses tend to be very ragged in this region, probably since they
are made for humans(!).  Be sure to get curves for the models you are
interested in.

Also note that simple speaker power-handling specs can be misleading in a major
way, if they assume that the speaker is used to reproduce music, and they state
the power applied to a full-range system that uses that tweeter.  Assuming a
pink-noise power distribution that falls at 3 dB/oct, with the woofer using the
most power, the tweeter gets very little.

You may have to contact the maker directly for relevant data.  High-power
tweeters tend to be expensive ($40 US seems to be typical at
www.parts-express.com these days).  The last time I set up a system to do this
was 2007. I ordered one each of 2 prospective models and ran my own tests. I
think they are out of production now.  The Pyramid TW47 was the one I chose.
It hit 121 dB SPL at 9 inches driven by 4 Vrms in 1/3rd octave around 10 kHz,
or 118 dB with a full octave at 16 kHz.

Hope this helps!

Bob Masta


-------------------------
On 11 Feb 2021 at 11:12, Boris Gourévitch wrote:

> Dear auditory list,
>
> I was looking for a speaker (probably a tweeter) that would reach 120 to
> maybe 130 dB SPL in a high frequency range (for mice).
>
> I am a bit puzzled with the many papers inducing noise trauma (i.e.
> Warren, Fenton et al, J Neuroscience 2020; Amanipour et al, 2018; Chen,
> Sheppar and Salvi 2016; Novak, Zelenka et al, 2016) which actually used
> pretty common tweeters to do that. Technical specifications for these
> tweeters do not really indicate that they could handle such high SPL
> (and therefore such high voltage). How did they determine that ? How can
> we know then ? Only by sensitivity measure adjusted for the watt power
> of the speaker ?
>
> Let's take an example: in the Warren et al above cited, the Visaton
> speaker from RadioSpare is used to deliver 3kHz at 126 dB SPL. The
> technical specifications
> (https://docs.rs-online.com/170c/0900766b802e5b23.pdf) indicate 30W max
> and a sensitivity of 86 dB. Thus, it seems that this speaker could not
> deliver above 101 dB SPL. How did the authors do to avoid damaging their
> speaker ?
>
> Same question with other speakers as well. I'm not an
> acoustician/electronician and I am probably missing something here.
>
> Many thanks for your help. Also, many of the tweeters from the papers
> above are discontinued so if you know a pretty robust one that you are
> safely using at high SPLs, please do not hesitate to tell me.
>
> Best regards
>
> Boris
>
> --
> Dr Boris Gourévitch
> CNRS Researcher
>
> Institut de l'Audition
> UMR1120 Inserm, Institut Pasteur
> 63 rue de Charenton
> 75012 Paris, France
>
> Tel: (+33) 1 76 53 50 41
>
> Personal Web page: http://www.pi314.net/
>
>
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