Considerations for “Contained” Studies in Laboratory or Captive Settings

Acoustic research on fishes and invertebrates conducted in the animals’ natural environment provides behavioral and environmental authenticity, incorporating realistic sound exposure and propagation scenarios. However, this work can be physically challenging and costly to implement. In contrast, lab-based studies using tanks or other enclosures are often cost effective and less time consuming. Lab-based studies also afford a high level of experimental control for conditions such as water temperature and light exposure. Sex, age, and other individual characteristics for test subjects may be determined, something that is often challenging in the field, as marine animals can be hard to see and follow.

Lab-based studies on fishes and invertebrates are often conducted using tanks, pools, and net pens of different sizes and shapes, in laboratories, or outdoors. Every component of a research setup can affect its acoustics and the results. For example, tanks and their supporting foundations are made of a variety of materials, all of which have different acoustic properties. Pools can be on a surface or dug into the ground. Net pens are submerged cages that allow water to flow freely. Sound sources and other devices may also be placed inside or outside any setup.

It is also important to recognize that the conditions inside an enclosure are distinctly different from that of the natural environment, and this is a critical limitation to lab-based studies. If proper considerations are not made, the acoustic field within the enclosure can become very complicated and difficult to characterize, and results may become confounded, reflecting the artificial sound field created, not the desired treatment[1]Carroll, A. G., Przeslawski, R., Duncan, A., Gunning, M., & Bruce, B. (2017). A critical review of the potential impacts of marine seismic surveys on fish & invertebrates. Marine Pollution Bulletin, 114(1), 9–24. https://doi.org/10.1016/j.marpolbul.2016.11.038[2]Duncan, A. J., Lucke, K., Erbe, C., & McCauley, R. D. (2016). Issues associated with sound exposure experiments in tanks. 070008. https://doi.org/10.1121/2.0000280[3]Jézéquel, Y., Bonnel, J., Aoki, N., & Mooney, T. A. (2022). Tank acoustics substantially distort broadband sounds produced by marine crustaceans. The Journal of the Acoustical Society of America, 152(6), 3747–3755. https://doi.org/10.1121/10.0016613[4]Jones, I. T., Stanley, J. A., Bonnel, J., & Mooney, T. A. (2019). Complexities of tank acoustics warrant direct, careful measurement of particle motion and pressure for bioacoustic studies. 010005. https://doi.org/10.1121/2.0001073[5]Parvulescu, A. (1967). The acoustics of small tanks. Marine Bio Acoustics, 2, 7–13[6]Popper, A. N., & Hawkins, A. D. (2018). The importance of particle motion to fishes and invertebrates. The Journal of the Acoustical Society of America, 143(1), 470–488. https://doi.org/10.1121/1.5021594[7]Popper, A. N., & Hawkins, A. D. (2021). Fish hearing and how it is best determined. ICES Journal of Marine Science, 78(7), 2325–2336. https://doi.org/10.1093/icesjms/fsab115[8]Rogers, P. H., Hawkins, A. D., Popper, A. N., Fay, R. R., & Gray, M. D. (2016). Parvulescu Revisited: Small Tank Acoustics for Bioacousticians. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 933–941). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_115. Additionally, animals may behave differently in tanks, pens, and pools than in the natural environment, even in response to the same sounds. A substantial factor is that movement is restricted in an enclosed environment.

Sound is often described in terms of sound pressure and particle motion, the latter of which is a vector field with direction (for more information, please see What components of sound are used for hearing?). Fishes and some marine invertebrates detect particle motion. Some fishes also detect sound pressure.

In the absence of boundaries (e.g., in the free-field) the sound pressure from a source decreases as distance from the source increases. Far from the source (“far field’) acoustic pressure and particle velocity are equal. Closer to the source (“near field”), the particle velocity component of sound has more energy. However, in an enclosed environment, sound movement (propagation) becomes more complicated and sound pressure and particle motion do not share the same relationship as they do in open water[9]Campbell, J., Shafiei Sabet, S., & Slabbekoorn, H. (2019). Particle motion and sound pressure in fish tanks: A behavioural exploration of acoustic sensitivity in the zebrafish. Behavioural Processes, 164, 38-47. https://doi.org/10.1016/j.beproc.2019.04.001[10]Rogers, P. H., Hawkins, A. D., Popper, A. N., Fay, R. R., & Gray, M. D. (2016). Parvulescu Revisited: Small Tank Acoustics for Bioacousticians. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 933–941). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_115.

Considerations must also be made for measuring sound pressure and particle motion[11]Gray, M. D., Rogers, P. H., Popper, A. N., Hawkins, A. D., & Fay, R. R. (2016). “Large” Tank Acoustics: How Big Is Big Enough? In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 363–369). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_43[12]Jones, I. T., Stanley, J. A., Bonnel, J., & Mooney, T. A. (2019). Complexities of tank acoustics warrant direct, careful measurement of particle motion and pressure for bioacoustic studies. 010005. https://doi.org/10.1121/2.0001073[13]Popper, A. N., & Hawkins, A. D. (2018). The importance of particle motion to fishes and invertebrates. The Journal of the Acoustical Society of America, 143(1), 470–488. https://doi.org/10.1121/1.5021594. Sound pressure can be measured with a hydrophone in the water, however, vector sensors, such as geophones or accelerometers, should be used to detect particle motion and its spatial components.

Small tank acoustics are therefore, very complicated, difficult to measure, and do not mimic the natural environment[14]Parvulescu, A. (1967). The acoustics of small tanks. Marine Bio Acoustics, 2, 7–13[15]Rogers, P. H., Hawkins, A. D., Popper, A. N., Fay, R. R., & Gray, M. D. (2016). Parvulescu Revisited: Small Tank Acoustics for Bioacousticians. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 933–941). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_115. The walls and floor of a tank or pool, as well as the water surface, act as reflective boundaries, which can lead to reverberation. This reverberation can impact signal length as well as received levels[16]Jézéquel, Y., Bonnel, J., Aoki, N., & Mooney, T. A. (2022). Tank acoustics substantially distort broadband sounds produced by marine crustaceans. The Journal of the Acoustical Society of America, 152(6), 3747–3755. https://doi.org/10.1121/10.0016613. For example, signals with acoustic wavelengths larger than the tank size can produce standing waves in the tank with constructive and destructive interference patterns (see Propagation from a sound source array for more details). Standing waves occur when the frequency of the acoustic signal equals its natural frequency, which is known as resonance. These patterns have “hot spots” and “low spots” which make it difficult to understand to what an animal is exposed. When animals are placed in a tank, they further change the acoustic field. Even in large tanks or pools, the sound field generated can be transformed by boundary interactions and can vary rapidly as a function of both space and frequency[17]Bart, A. N., Clark, J., Young, J., & Zohar, Y. (2001). Underwater ambient noise measurements in aquaculture systems: A survey. Aquacultural Engineering, 25(2), 99–110. https://doi.org/10.1016/S0144-8609(01)00074-7[18]Gray, M. D., Rogers, P. H., Popper, A. N., Hawkins, A. D., & Fay, R. R. (2016). “Large” Tank Acoustics: How Big Is Big Enough? In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 363–369). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_43.

Thickening tank walls or otherwise changing tank walls has little to no effect on the resonance frequencies that can be produced. Adding materials around tank walls to dampen the effect may influence high frequencies but would cause no effect at lower frequencies (Akamatsu et al. 2002; Popper and Hawkins 2018; and Gray 2016).

Net pens can provide a more realistic experimental environment. However, additional environmental sounds may be added unexpectedly to the sound field from the local environment (e.g., snapping shrimp, human and boating noise associated with servicing net-pens, distant shipping, etc.), thereby potentially impacting the overall sound field.

Researchers conducting acoustic assessments in laboratory settings, as well as individuals interpreting research results, need to be aware of the above constraints when using tanks, pools, and other enclosures. Results should be interpreted in the context of these experimental limitations; it can often be difficult to translate results to the natural environment[19]Rogers, P. H., Hawkins, A. D., Popper, A. N., Fay, R. R., & Gray, M. D. (2016). Parvulescu Revisited: Small Tank Acoustics for Bioacousticians. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 933–941). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_115[20]Popper, A. N., & Hawkins, A. D. (2018). The importance of particle motion to fishes and invertebrates. The Journal of the Acoustical Society of America, 143(1), 470–488. https://doi.org/10.1121/1.5021594[21]Popper, A. N., Hice-Dunton, L., Jenkins, E., Higgs, D. M., Krebs, J., Mooney, A., Rice, A., Roberts, L., Thomsen, F., Vigness-Raposa, K., Zeddies, D., & Williams, K. A. (2022). Offshore wind energy development: Research priorities for sound and vibration effects on fishes and aquatic invertebrates. The Journal of the Acoustical Society of America, 151(1), 205–215. https://doi.org/10.1121/10.0009237. Several publications[22]Akamatsu, T., Okumura, T., Novarini, N., & Yan, H. Y. (2002). Empirical refinements applicable to the recording of fish sounds in small tanks. The Journal of the Acoustical Society of America, 112(6), 3073–3082. https://doi.org/10.1121/1.1515799[23]Gray, M. D., Rogers, P. H., Popper, A. N., Hawkins, A. D., & Fay, R. R. (2016). “Large” Tank Acoustics: How Big Is Big Enough? In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 363–369). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_43[24]Jézéquel, Y., Bonnel, J., Aoki, N., & Mooney, T. A. (2022). Tank acoustics substantially distort broadband sounds produced by marine crustaceans. The Journal of the Acoustical Society of America, 152(6), 3747–3755. https://doi.org/10.1121/10.0016613[25]Popper, A. N., & Hawkins, A. D. (2018). The importance of particle motion to fishes and invertebrates. The Journal of the Acoustical Society of America, 143(1), 470–488. https://doi.org/10.1121/1.5021594 outline recommendations for acoustical measurements in tanks, including terminology, methods, and metrics. Key recommendations include:

  • Characterizing the acoustic sound field in three dimensions prior to starting experimental activities.
  • Measuring sound pressure, particle motion, and substrate vibration (when applicable).
  • Measuring particle motion directly (not derived) in tank-based studies.
  • Reducing sounds associated with motors, aeration, water pumps, and other equipment in an indoor setting[26]Bart, A. N., Clark, J., Young, J., & Zohar, Y. (2001). Underwater ambient noise measurements in aquaculture systems: A survey. Aquacultural Engineering, 25(2), 99–110. https://doi.org/10.1016/S0144-8609(01)00074-7[27]Davidson, J., Frankel, A. S., Ellison, W. T., Summerfelt, S., Popper, A. N., Mazik, P., & Bebak, J. (2007). Minimizing noise in fiberglass aquaculture tanks: Noise reduction potential of various retrofits. Aquacultural Engineering, 37(2), 125–131. https://doi.org/10.1016/j.aquaeng.2007.03.003.

Lastly, adequate replication is key for any experimental design and, when possible, complementary research in the field is recommended to compare, validate, and better understand laboratory findings[28]Campbell, J., Shafiei Sabet, S., & Slabbekoorn, H. (2019). Particle motion and sound pressure in fish tanks: A behavioural exploration of acoustic sensitivity in the zebrafish. Behavioural Processes, 164, 38–47. https://doi.org/10.1016/j.beproc.2019.04.001t[29]Carroll, A. G., Przeslawski, R., Duncan, A., Gunning, M., & Bruce, B. (2017). A critical review of the potential impacts of marine seismic surveys on fish & invertebrates. Marine Pollution Bulletin, 114(1), 9–24. https://doi.org/10.1016/j.marpolbul.2016.11.038[30]Gray, M. D., Rogers, P. H., Popper, A. N., Hawkins, A. D., & Fay, R. R. (2016). “Large” Tank Acoustics: How Big Is Big Enough? In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 363–369). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_43[31]Jézéquel, Y., Bonnel, J., Aoki, N., & Mooney, T. A. (2022). Tank acoustics substantially distort broadband sounds produced by marine crustaceans. The Journal of the Acoustical Society of America, 152(6), 3747–3755. https://doi.org/10.1121/10.0016613[32]Popper, A. N., & Hawkins, A. D. (2018). The importance of particle motion to fishes and invertebrates. The Journal of the Acoustical Society of America, 143(1), 470–488. https://doi.org/10.1121/1.5021594[33]Popper, A. N., Hice-Dunton, L., Jenkins, E., Higgs, D. M., Krebs, J., Mooney, A., Rice, A., Roberts, L., Thomsen, F., Vigness-Raposa, K., Zeddies, D., & Williams, K. A. (2022). Offshore wind energy development: Research priorities for sound and vibration effects on fishes and aquatic invertebrates. The Journal of the Acoustical Society of America, 151(1), 205–215. https://doi.org/10.1121/10.0009237[34]Slabbekoorn, H. (2016). Aiming for Progress in Understanding Underwater Noise Impact on Fish: Complementary Need for Indoor and Outdoor Studies. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 1057–1065). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_131.

Although enclosure-based studies are not a replacement for field-based work, certain types of acoustic studies may require a laboratory setting (e.g., some physiological studies). Tank studies may be useful when comparing responses within a single species under identical acoustical conditions.

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Cited References

Cited References
⇡1, ⇡29 Carroll, A. G., Przeslawski, R., Duncan, A., Gunning, M., & Bruce, B. (2017). A critical review of the potential impacts of marine seismic surveys on fish & invertebrates. Marine Pollution Bulletin, 114(1), 9–24. https://doi.org/10.1016/j.marpolbul.2016.11.038
⇡2 Duncan, A. J., Lucke, K., Erbe, C., & McCauley, R. D. (2016). Issues associated with sound exposure experiments in tanks. 070008. https://doi.org/10.1121/2.0000280
⇡3, ⇡16, ⇡24 Jézéquel, Y., Bonnel, J., Aoki, N., & Mooney, T. A. (2022). Tank acoustics substantially distort broadband sounds produced by marine crustaceans. The Journal of the Acoustical Society of America, 152(6), 3747–3755. https://doi.org/10.1121/10.0016613
⇡4, ⇡12 Jones, I. T., Stanley, J. A., Bonnel, J., & Mooney, T. A. (2019). Complexities of tank acoustics warrant direct, careful measurement of particle motion and pressure for bioacoustic studies. 010005. https://doi.org/10.1121/2.0001073
⇡5, ⇡14 Parvulescu, A. (1967). The acoustics of small tanks. Marine Bio Acoustics, 2, 7–13
⇡6, ⇡13 Popper, A. N., & Hawkins, A. D. (2018). The importance of particle motion to fishes and invertebrates. The Journal of the Acoustical Society of America, 143(1), 470–488. https://doi.org/10.1121/1.5021594
⇡7 Popper, A. N., & Hawkins, A. D. (2021). Fish hearing and how it is best determined. ICES Journal of Marine Science, 78(7), 2325–2336. https://doi.org/10.1093/icesjms/fsab115
⇡8 Rogers, P. H., Hawkins, A. D., Popper, A. N., Fay, R. R., & Gray, M. D. (2016). Parvulescu Revisited: Small Tank Acoustics for Bioacousticians. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 933–941). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_115
⇡9 Campbell, J., Shafiei Sabet, S., & Slabbekoorn, H. (2019). Particle motion and sound pressure in fish tanks: A behavioural exploration of acoustic sensitivity in the zebrafish. Behavioural Processes, 164, 38-47. https://doi.org/10.1016/j.beproc.2019.04.001
⇡10, ⇡15 Rogers, P. H., Hawkins, A. D., Popper, A. N., Fay, R. R., & Gray, M. D. (2016). Parvulescu Revisited: Small Tank Acoustics for Bioacousticians. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 933–941). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_115
⇡11, ⇡18 Gray, M. D., Rogers, P. H., Popper, A. N., Hawkins, A. D., & Fay, R. R. (2016). “Large” Tank Acoustics: How Big Is Big Enough? In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 363–369). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_43
⇡17 Bart, A. N., Clark, J., Young, J., & Zohar, Y. (2001). Underwater ambient noise measurements in aquaculture systems: A survey. Aquacultural Engineering, 25(2), 99–110. https://doi.org/10.1016/S0144-8609(01)00074-7
⇡19 Rogers, P. H., Hawkins, A. D., Popper, A. N., Fay, R. R., & Gray, M. D. (2016). Parvulescu Revisited: Small Tank Acoustics for Bioacousticians. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 933–941). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_115
⇡20, ⇡25, ⇡32 Popper, A. N., & Hawkins, A. D. (2018). The importance of particle motion to fishes and invertebrates. The Journal of the Acoustical Society of America, 143(1), 470–488. https://doi.org/10.1121/1.5021594
⇡21, ⇡33 Popper, A. N., Hice-Dunton, L., Jenkins, E., Higgs, D. M., Krebs, J., Mooney, A., Rice, A., Roberts, L., Thomsen, F., Vigness-Raposa, K., Zeddies, D., & Williams, K. A. (2022). Offshore wind energy development: Research priorities for sound and vibration effects on fishes and aquatic invertebrates. The Journal of the Acoustical Society of America, 151(1), 205–215. https://doi.org/10.1121/10.0009237
⇡22 Akamatsu, T., Okumura, T., Novarini, N., & Yan, H. Y. (2002). Empirical refinements applicable to the recording of fish sounds in small tanks. The Journal of the Acoustical Society of America, 112(6), 3073–3082. https://doi.org/10.1121/1.1515799
⇡23, ⇡30 Gray, M. D., Rogers, P. H., Popper, A. N., Hawkins, A. D., & Fay, R. R. (2016). “Large” Tank Acoustics: How Big Is Big Enough? In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 363–369). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_43
⇡26 Bart, A. N., Clark, J., Young, J., & Zohar, Y. (2001). Underwater ambient noise measurements in aquaculture systems: A survey. Aquacultural Engineering, 25(2), 99–110. https://doi.org/10.1016/S0144-8609(01)00074-7
⇡27 Davidson, J., Frankel, A. S., Ellison, W. T., Summerfelt, S., Popper, A. N., Mazik, P., & Bebak, J. (2007). Minimizing noise in fiberglass aquaculture tanks: Noise reduction potential of various retrofits. Aquacultural Engineering, 37(2), 125–131. https://doi.org/10.1016/j.aquaeng.2007.03.003
⇡28 Campbell, J., Shafiei Sabet, S., & Slabbekoorn, H. (2019). Particle motion and sound pressure in fish tanks: A behavioural exploration of acoustic sensitivity in the zebrafish. Behavioural Processes, 164, 38–47. https://doi.org/10.1016/j.beproc.2019.04.001
⇡31 Jézéquel, Y., Bonnel, J., Aoki, N., & Mooney, T. A. (2022). Tank acoustics substantially distort broadband sounds produced by marine crustaceans. The Journal of the Acoustical Society of America, 152(6), 3747–3755. https://doi.org/10.1121/10.0016613
⇡34 Slabbekoorn, H. (2016). Aiming for Progress in Understanding Underwater Noise Impact on Fish: Complementary Need for Indoor and Outdoor Studies. In A. N. Popper & A. Hawkins (Eds.), The Effects of Noise on Aquatic Life II (Vol. 875, pp. 1057–1065). Springer New York. https://doi.org/10.1007/978-1-4939-2981-8_131