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Hi Bioacoustic community,

We have been doing several experiments in fish tanks to identify fish sounds. However, the resonance degrades a lot the signal recorded with the hydrophone. The resonance frequencies depend on the dimension of the tank and can be dampen with anechoic panels. Our frequency range of interest is 0-1Khz (ideally 1-8kHz): this give us a guideline for the tank dimension. Besides, the size of our tank should be smaller than 1meter x 1m x1m. We will work both with sea water and fresh water.

I have been searching for some papers about how to design a tank for acoustic experiment and what material we should use. I found only information for rooms... Does somebody already made such a fish tank? Do you have any tips to calculate the resonance frequencies? Do you know what material we could use to dampen the resonance inside the tank? How could we isolate the tank from outside noise?

Any information would help! Thanks in advance.

Julia Wiel

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3 Answers 3

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IMO, a lot depends on the type of sound, and experiment you wanted to carry out.

I see two different issues:

  • resonance that can occur for lengthy tonal and tank linear dimensions of wavelength/2 (e.g: 1 khz resonance for 75 cm tank).
  • reflections of any type of signals, which is more serious. This is highly geometry dependent but in such a small tank you will have reflections < 0.1ms (0.1ms corresponds to 15 cm reflection delay length). As outside tank is air, any reflection will be phase-reversed and most likely reduce fish call signal

Acoustic measurement tanks (e.g. for hydrophone calibrations) are usually much larger (LWH = 4m x 3m x 2m or larger) and are limited to frequencies >1 kHz. So, for lower frequencies I would expect much larger water masses.

Edit: Concerning reflection: One must consider at least three paths:

  • direct path from fish to hydrophone
  • reflected path via boundary close to fish
  • reflected path via boundary close to hydrophone

To avoid reflections, the travel time difference between reflected path and direct path must be greater than length of fish call to avoid interferences.

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  • $\begingroup$ Good to remind that resonance and reflection are distinct effects. - resonance: so, for the tank dimension, the minimal side should be superior at the wavelength of the signal I am studying divided by two? min(x,y,z)>wavelength/2 Do you use the frequency peak to calculate the wavelength? - reflection: I understand the phase-reversed part but not the first part of your answer. What do you call 15 cm reflection delay? Does "reflection<0.1ms" mean that a signal need less than 0.1ms to travel, hit the wall, and come back to its source? $\endgroup$
    – Julia Wiel
    Commented Nov 23, 2022 at 15:24
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Good morning Julia,

I was once interested in recording underwater calling frogs, and remember reading the following article:

Okumura, T., Akamatsu, T., & Yan, H. Y. (2002). Analyses of small tank acoustics: empirical and theoretical approaches. Bioacoustics, 12(2-3), 330-332.

I hope the formulas and measurements there will be helpful for your fish recordings!

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  • $\begingroup$ This article is pertinent for the measurements. It provides good exemples of calculation for the resonance frequencies of rectangular and cylandrical tanks. The comment about the dependance between the tank size, the resonance frequency, and the fish call frequency range gives an idea of what dimensions could fit my experiment. Thanks Matías! $\endgroup$
    – Julia Wiel
    Commented Nov 23, 2022 at 14:50
  • $\begingroup$ Hi Matias, could you edit your response to summarize how this paper responds to the question please (or cite the abstract etc)? This would be very helpful for readers. $\endgroup$
    – Noil
    Commented Nov 24, 2022 at 9:11
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there are a lot of papers about this in the fish acoustics literature, for example:

Rogers, P. et al. (2016) ‘Parvulescu revisited: Small tank acoustics for bio-acousticians’, in Hawkins, A. D. and Popper, A. N. (eds) The Effects of Noise on Aquatic Life II. New York, NY: Springer , pp. 933–941.

Akamatsu, T. et al. (2002) ‘Empirical refinements applicable to the recording of fish sounds in small tanks’, Journal of the Acoustical Society of America, 112, pp. 3073–3082.

And the one always cited regarding this:

Parvulescu, A. (1964) ‘The acoustics of small tanks’, in Tavolga, W. N. (ed.) Marine Bio-Acoustics. Oxford: Pergamon Press, pp. 7–13.

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