Acousonde™ FAQ (Applications)

Acousonde™ Applications Questions

Updated 17 June 2011

Marine wildlife

Will it work for my species and in my environment?

Only you, as the biologist, can assess whether the Acousonde's configuration satisfies the requirements of working with your species. Three key characteristics of the Acousonde, however, will affect its applicability in your environment.

First, this is an archival tag, meaning that it must be physically recovered for you to retrieve its data.

Second, the Acousonde 3A includes no attachment, flotation, tracking, or retrieval equipment, meaning that you must supply all of these for the 3A. The Acousonde 3B, on the other hand, incorporates suction-cup attachment, flotation, retrieval strobe, and a receptacle for a third-party VHF retrieval transmitter.

Third, the Acousonde's usefulness may be seriously impacted by flow or attachment noise; if your application environment involves banging, creaking, vibration, or strong, poorly faired flow, your acoustic records may be contaminated with noise. Severe contamination can render your acoustic data useless.

If it requires recovery, how do I recover it?

For some species, such as blue whales, recovery presents a major obstacle. First, you must be certain the tag and attachment assembly will float! Second, you must have a way of knowing where the tag is after it leaves the subject. The typical approach is to incorporate a separate VHF transmitter in the tag assembly. VHF wildlife transmitters can be detected from distances of 20 miles or more, provided your receiver can be located at higher elevation (a building, hillside, or aircraft) and in an area of low electromagnetic noise (the bridge of a research vessel may not qualify). However, while a VHF transmitter or something like it is a necessity to find the tag when it is within a few miles of you, it does not help you if the tag is out of range. Long-distance tracking requires a satellite transmitter; note that adding satellite-tracking capability to the Acousonde will require extensive custom development.

The Acousonde 3B incorporates a strobe that can improve nighttime retrieval capability.

How do I attach acoustic recording tags to my subject?

That's up to you. The A-series Acousonde (Model B003A) is designed to be as broadly useful as possible. You can attach it with suction cups, crossbow, or glue; however, as the expert with your species, you must develop the most suitable attachment approach. Model B003A comes with no attachment gear. Model B003B, on the other hand, incorporates a low-profile suction-cup attachment system.

Note: serious ethical, legal and personal-safety issues accompany any attempt to attach tags to wild or protected animals. This short discussion of attachment alternatives is not intended to downplay the responsibilities and risks associated with this activity. You are responsible for obtaining the necessary permits and conducting your research with the utmost concern for your safety and the safety of your associates and subjects.

How long can an attachment last on an animal?

The duration of attachment depends on the attachment technique. To date, attachment methods have included suction cups (whales), glue (seals), tethers (manatees) and surgical implantation (sharks). These techniques have yielded attachment lifetimes from a few minutes to several weeks. To our knowledge nobody has used the Acousonde with a dorsal-fin saddle.

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Differences between the Acousonde 3A and the Acousonde 3B

Do the 3A and the 3B differ electronically?: Yes. The 3B includes an ambient light sensor and a retrieval strobe. The light sensor serves primarily to restrict flashing of the strobe to nighttime; however, it is also tied to the auxiliary sampling system so that future firmware may record ambient light level. Another difference is that the 3B only provides 2 MicroSD storage-card slots, while the 3A provides 4 (in most cases battery limitations and the large capacities of modern MicroSD cards renders this difference moot). Finally, the 3B omits some extra components and debugging ports that the 3A supports for non-wildlife applications.
Do the 3A and the 3B differ acoustically?: Yes. While the 3A and the 3B offer identical hydrophone configurations, the high-frequency hydrophone option will respond more uniformly in the 3A than in the 3B. Limited space in the 3B requires the hydrophones to be placed adjacent to the pressure housing for the battery. This shouldn't be an issue for the lower frequencies monitored by the low-power hydrophone, but the presence of an air body near the high-frequency hydrophone may significantly affect its directionality.

Permitting information

What are the precise dimensions and weight of the Acousonde 3A?: The Model B003A cylindrical Acousonde ("Acousonde 3A") with a battery cap and A-size lithium battery but WITHOUT flotation, attachment, or recovery gear, weighs 262 g (in air) in a volume of 172 cc (this compares to 212 g and 135 cc for the Model B002B Bioacoustic Probe). The "torpedo" shape is 3.2 cm in diameter and 22.1 cm long (compared with 3.2 cm and 19.3 cm for the Bioacoustic Probe). It is negatively bouyant; in seawater the tag weighs approximately 86 g (compared with 74 g for the Bioacoustic Probe). Of course, flotation, attachment and recovery gear will add to the size and weight of your total package. Please also see the Acousonde 3A PDF brochure.
What are the precise dimensions and weight of the Acousonde 3B?: The Model B003B Acousonde ("Acousonde 3B") with battery cap, A-size lithium battery, flotation, quad suction cup attachment, retrieval strobe, and (separately-procured) VHF transmitter, weighs at most 360 g in air (substituting a single suction cup for the four separate suction cups may add as much as 31 g in air, but only 3 g when submerged in seawater). The 3B hydrodynamic shape is 4.2 cm high (including uncompressed suction cups), 7.9 cm wide at its widest point, and 22.4 cm long (not counting the VHF transmitter or the retrieval strobe that protrudes an additional 1.7 cm from the end of the attached float). The 3B is positively buoyant, with a buoyancy in seawater no less than 50 g. The downloads area provides a detailed diagram of the Acousonde 3B as well as a one-page PDF brochure with specifications.

General attachment/deployment guidelines

What VHF transmitter is recommended for the Acousonde 3A?: The Acousonde 3A comes with no flotation, attachment, or retrieval gear. This third-party equipment, not the size or shape of the Acousonde 3A itself, will drive the choice of VHF transmitter. Please correspond with your source of this gear regarding a VHF transmitter.
To make direction-finding easier, some field biologists specify a custom VHF pulse rate of 120 ppm (pulses per minute) and a custom pulse width of 25 ms (55 ppm and 20 ms are typical manufacturer defaults). Users must also specify a frequency band compatible with the VHF receiving equipment they plan to use.
What VHF transmitter is recommended for the Acousonde 3B?: The Acousonde 3B float provides a receptacle 17.85 mm (0.703") in diameter by 50.8 mm (2.00") deep designed for an Advanced Telemetry Systems (ATS) model F1835B bottle-shape implant transmitter, modified at the ATS factory with a stiff antenna as used in their backmount transmitters. Note that ATS transmitter dimensions and weight can vary from batch to batch, so if you order from ATS, please insist that the above diameter is the "absolute maximum" diameter, and specify that the transmitter weight, including antenna, must not exceed 26 g in air.
To make direction-finding easier, some field biologists additionally specify a custom VHF pulse rate of 120 ppm (pulses per minute) and a custom pulse width of 25 ms (ATS transmitters typically default to 55 ppm and 20 ms). Users must also specify a frequency band compatible with the VHF receiving equipment they plan to use.
What does the Acousonde 3A mechanically provide to secure attachment or retrieval gear?: Model B003A includes a cylindrical battery cap with a 10-24 threaded screw-hole at the center; this can be used to secure eyebolts with 10-24 threads (for tethers) or to attach flotation. A urethane "key" protruding from the Acousonde's surface can be used to prevent screw-on flotation from rotating unintentionally. Attachment systems such as suction cups must be secured either to the flotation (not included) or to the urethane body of the Acousonde itself. This has been done in the past with gear as simple as cable ties and electrical tape.
Seawater contact with steel bolts or eyebolts secured in the aluminum battery housing will cause galvanic corrosion. Eventually this corrosion may permanently fuse the two metals together. To avoid this, coat the threads before assembly with an anti-seize product such as Loctite Marine Grade Anti-Seize. Alternately, use an aluminum or nylon bolt.
What are the best locations for securing the Acousonde 3A?: Attachments must avoid stress to sensitive components. The three most fragile components are the main (low-power) hydrophone, the high-frequency hydrophone (if that option is present), and the pressure transducer. The photograph in the Acousonde 3A PDF brochure identifies the locations of these components. The two recommended regions for attachment strapping are (a) the battery housing and (b) the bank of flash memory cards situated between the two hydrophones.
I want to launch the Acousonde onto a target. Can it handle the impact?: Unknown. The Acousonde 3A shares its basic mechanical design with its predecessor, the Bioacoustic Probe, and that earlier instrument took abuse well. However until recently no customer has ever asked about high-speed impact tolerance, so it was not part of the Acousonde's design criteria. To recommend the Acousonde for use in these applications, we would need to perform potentially destructive testing that would very probably indicate a need for additional development. Given the expense of this testing and development, demand will determine our ability to support high-speed impact applications.

Understanding acoustic recording tags

Why can't acoustic recording tags telemeter their data in real time?: The Acousonde samples acoustic data at rates up to 232 or possibly even 464 kilohertz. To be useful, it must gather hours of recordings, potentially adding up to several gigabytes of data. There is no way to transmit this vast amount of data by satellite or radio, especially from a low-power device that spends most of its time submerged. However, if a tag designer knows up front exactly what sort of signal is of interest, the tag may be designed with special-purpose hardware and/or software to detect, characterize, and count occurrences of that signal. In this case telemetry may be possible since the acoustic data will be heavily preprocessed and compressed on board the tag.
How does the Acousonde differ from other acoustic tags?: The Acousonde, strictly speaking, is not an "acoustic tag." For decades, the fish-biology community has used the term "acoustic tag" to refer to active "pinger" tags that produce ultrasonic pulses. These pulses allow researchers with detection equipment to follow the tagged subject. The Acousonde, on the other hand, passively acquires acoustic data. It does not transmit ultrasonic pulses. We advocate calling passive-acoustic tags such as the Acousonde "bioacoustic tags" or "acoustic recording tags" to reduce confusion.
OK, how does the Acousonde differ from other BIOacoustic tags?: The two key differences between the Acousonde and many other acoustically-related tags are: (1) the Acousonde is designed to allow application by small, tight-budget biology teams without requiring extensive training or the presence of an engineering specialist; and (2) the Acousonde is a broadband acoustic recorder. It digitizes and records full acoustic waveforms, and does not include any detection or compression hardware such as pulse detection (although such capabilities may be implemented in future firmware releases). As such it is substantially more complex and requires more processing power, a larger battery, and greater data capacity than a pulse detector.