Bioacoustic Probe FAQ

How available is the B-Probe? Can I get one right now?: Production has ceased on the B002B model Bioacoustic Probe, and all inventory has been sold. Prototypes of a new and much more powerful design (B003A model) are in assembly as of this writing (5 November 2007) but much work remains before we can quote specifications, options, pricing, or delivery. We hope to make the new design commercially available in the second half of 2008.
How much does the B-Probe cost?: Please contact Acoustimetrics. US government and volume discounts are available. Please be aware that the Bioacoustic Probe is a custom-made, professional research instrument.
What are the precise dimensions and weight?: The (now no longer available) B-series Bioacoustic Probe with a tapered battery cap, with battery but WITHOUT flotation, attachment, or recovery gear, weighs 200 g (in air) in a volume of 131 cc. Users who want to attach flotation will probably need the larger cylindrical battery cap that provides a threaded screw-hole; in this configuration the Probe weighs 212 g in air and displaces 135 cc. Its cylindrical "torpedo" shape is 3.2 cm in diameter and 19.3 cm long. It is negatively bouyant; in seawater the tag weighs approximately 66 g (tapered cap) or 74 g (cylindrical cap). Of course, flotation, attachment and recovery gear will add to the size and weight of your total package.
Does the B-Probe come with deployment and tracking gear, like a VHF beacon?: Not at this time. Our goal has been to make the Bioacoustic Probe adaptable to many species. We have not attempted to research and develop flotation, attachment, or recovery technology for each species of possible interest. Cetacean Research Technology has developed suction-cup deployment systems for using the B-Probe with large whales; you may wish to contact them.
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How does the B-Probe differ from other acoustic tags?: The Bioacoustic Probe, 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 Bioacoustic Probe, on the other hand, passively acquires acoustic data. It does not transmit ultrasonic pulses. We advocate calling passive-acoustic tags such as the B-Probe "bioacoustic tags" or "acoustic recording tags" to reduce confusion.
OK, how does the B-Probe differ from other BIOacoustic tags?: Bioacoustic-tag technology is still extremely young. All bioacoustic-tag programs, including ours, have a strong experimental flavor as the wildlife continue to teach us how to do this properly. Within this experimental context, the B-Probe's design has focused on ease-of-use, reliability, and the potential for long deployments, on the order of days, weeks, or months. A critical goal was to enable field biologists to apply the B-Probe without needing extensive training or the presence of a specialist. The B-Probe was developed specifically to address the issue of how low-frequency acoustic stimuli may affect a subject, and is not well suited for measuring high-frequency vocalizations such as those of dolphins and sperm whales. The B-Probe measures temperature, pressure, and (optionally) 2-D tilt/acceleration, but does not at present provide any compassing ability. We hope to increase the capabilities of the B-Probe in the future.
What's the highest frequency the B-Probe can record?: Software limits an off-the-shelf B-Probe to recording frequencies up to 7.4 kHz (20 kHz sampling rate). Sampling at this rate draws heavily on the battery, however, and at colder temperatures typical batteries may not be able to maintain an output voltage sufficient to run the instrument. Sampling rates below 10 kHz are more sustainable at lower temperatures.
Can you increase the sampling rate?: We are working on this for the new version of the Bioacoustic Probe targeted for availability in the second half of 2008. We expect maximum sample rates of at least 200 kHz.
How quiet are the recordings? Are there noise problems?: The anti-alias filter embedded in the electronics produces an unavoidable broadband noise with an RMS level of approximately the lowest two bits (out of a sixteen-bit resolution). In addition to this broadband noise, digital signals on the board couple a tonal artifact into the digitized acoustic record [As of serial number 026 this tone has been eliminated]. The amplitude of this tone depends on the choice of sampling rate, however, it typically does not occupy more than the lowest three bits, and is located in frequency above the anti-alias cutoff frequency. Given flow-related noise levels typical of attachment to wildlife, these noise sources should be negligible. They may affect moored or seafloor applications, however, especially in very quiet environments.
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Why can't the B-Probe telemeter its data? Recoverable tags are a pain.: The B-Probe samples acoustic data at rates up to several kilohertz. To be useful, it must gather hours of recordings, adding up to hundreds of megabytes of data. There is no way to transmit this large amount of data by satellite or radio, especially from a low-power device that spends most of its time submerged. In the future, when more is known about what specific features of sound exposure are important, it may be possible for tags to compress acoustic data to the extent that telemetry may be possible.
Aren't infrared connections slow? How long does it take to download data?: The B-Probe uses the Standard InfraRed (SIR) physical specification, with real measured transfer rates of up to 5.3 kilobytes per second. This transfer rate is comparable to that of an excellent phone line. At this rate, a half-gigabyte of data will require almost 30 hours to download from the B-Probe to a personal computer. While this relatively slow transfer rate is not ideal, significantly faster rates would not be possible with the low-power processor at the heart of the design. Remember also that you can choose to download selected portions of stored data, which of course will require less time. The new design in progress will use full-speed USB which we expect to be about 100 times faster.
Wouldn't an electrical download connection be much faster?: Not necessarily. The B-Probe relies on a very slow 16-MHz low-power processor which is not capable of moving data quickly by either electrical or optical means. Also, electrical connectors can be unreliable and have have a short service life when used in a marine environment.
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How do I attach the B-Probe to my subject?: That's up to you. The B-Probe 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. The B-Probe comes with no attachment gear. 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 do I recover the B-Probe after getting it on a free-ranging animal?: 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 beacon in the tag assembly. VHF wildlife beacons 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 beacon 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. In cases like this you will need a satellite transmitter. Important: developing an attachment and recovery system incorporating a satellite transmitter, VHF beacon, flotation, and B-Probe in an single assembly that is both easy to attach AND acoustically quiet is a very difficult challenge. Do not leave this part of your project until the last minute! At present the B-Probe comes with no attachment or recovery gear.
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What computer and operating system are required to download data?: The B-Probe uses the IrOBEX infrared file transfer protocol. Native support for this protocol is available under Windows 2000 and newer Windows operating systems, so that data can be transferred directly to a Windows-based laptop computer via its built-in infrared port. This requires using a Palm to command the tag to download data, then placing the tag within infrared range of the notebook computer. For Apple Macintosh computers running the OS X operating system, infrared software is available that allows direct control of the downloading functions; this software provides a convenient and flexible alternative to downloading data under control of the Palm. Macs, and PC's that do not have an infrared port, also require the purchase of a USB-to-serial adapter and a serial-based infrared dongle. Note: Because Mac OS X does not natively support IrOBEX, one cannot use USB-to-infrared adapters with OS X for this purpose. A Keyspan USB-to-serial adapter together with an Actisys serial-to-infrared adapter are necessary to interact with the B-Probe under Mac OS X.
What about Linux? Can I download data with that?: No software has been developed to provide this capability under Linux. However, the OS X infrared software was written to use a unix-style command line interface, and should be portable to Linux.
Why not just download the data to the Palm?: It is possible, and encouraged, to download very small text files to the Palm, such as the log file and the filesystem directory. Larger files, however, may exceed the Palm's data capacity. In any event there is no Palm software available to view or analyze the data files that come off the tag.
I don't have a PalmOS-compatible PDA. Can I still use the B-Probe?: No. It is possible to program a personal computer to send command packets to the B-Probe, but at present this is only supported under OS X on the Macintosh, and only for downloading data, not for general command or interrogation. You must have a PalmOS-compatible personal digital assistant (PDA) with an infrared port to command the B-Probe.
What brand and model of PalmOS-compatible PDA should I get?: A bewildering variety of past and present PalmOS-compatible PDAs are fully compatible with the Bioacoustic Probe. It has been tested with the Palm III, V, m100, m500, Zire 21, and Palm TX, as well as models from Handspring and a Kyocera cell phone. Any recent PalmOS-compatible PDA should work. Replaceable batteries are a bonus for field work as no charger is necessary, but we are not aware of any current PalmOS PDAs that use replaceable batteries. We recommend that you choose a PDA on the basis of price and durability, as well as relevance to other tasks you may have for it.
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How do I import the data into software that can analyze them?: The tag stores and provides data in a custom format known as "MT" format. A MATLAB program (that is, an M-file) is available to read MT files directly into MATLAB. A free unsupported application for Apple's Mac OS X, "MT Viewer," is also available to read and inspect MT files on Macintosh personal computers; MT Viewer can also export selected data in MATLAB, ASCII, or WAV format. If neither MATLAB nor MT Viewer is an option for you, you may be able to convert MT files directly to WAV if you manually keep track of the sampling rate, and strip the leading 512-byte MT header using multipurpose audio-conversion software such as SoX . Otherwise, some custom translation software may need to be programmed; detailed information on MT format is available to facilitate such an effort. With time we hope to gather the translation tools that users have created and make them available to the community to minimize "wheel reinvention." We are also in communication with Cornell University to see if support for the MT format may be possible in future versions of Raven, the bioacoustic analysis software that has succeeded the popular Canary.
What exactly is MT format?: MT format is a very simple single-channel format for containing time-series data. It consists of a fixed-length 512-byte header followed by an arbitrary length of 2-byte samples. The header provides information on sampling rate, start time, site, title, comments, and calibration, among other things. All header fields are in ASCII, making the headers immune to byte-swapping issues and easy to read in low-level file editors.
Why not use WAV format?: WAV format is the de-facto standard for storing uncompressed audio on computers running Microsoft Windows. WAV was never intended to store scientific data, and does not provide a standardized means of storing calibration values, time of day, site codes, comments, or other "metadata" parameters essential to scientific purposes. Although WAV is not the best native format for scientific data, some analysis packages can accept WAV input, so a few B-Probe users have developed software to convert the B-Probe's native MT format to WAV. MT Viewer (see "How do I import the data" above) provides an export function that allows selected portions of data to be exported to WAV for analysis by other software.
I've never analyzed acoustic data. How do I get started?: Acoustic analysis is nearly impossible for a non-specialist to do in a repeatable, standards-based manner without formal education. This difficulty particularly affects studies requiring standardized calibrated data for regulatory purposes. Even with formal education it is surprisingly easy to use techniques that are inappropriate to the signal or situation in question, leading to meaningless and irreproducible results. The use of canned software only increases this risk. Partnering with an expert or formal education in physics and signal processing are the only two ways we can suggest for performing calibrated acoustic analysis. If you run canned software you will get numbers all right, but... A good way to know when you may be ready to analyze acoustic data on your own is when you fully understand the meaning of the unit designation "dB re 1 µPa/Hz^½".
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How long does the battery last?: The B-Probe was designed to fill a 1-GB storage unit at a 2 to 4 kHz sample rate with the smallest possible battery, in order to make the instrument suitable for the broadest possible size range of animal subjects. At sample rates below 2 kHz or above 4 kHz, the ability of the B-Probe to fill a 1-GB storage unit depends increasingly on temperature and on whether or not auxiliary channels (pressure, temperature, acceleration) are being sampled. For example, at a sample rate of 10 kHz with auxiliary sampling on, temperatures below 5°C may limit the B-Probe to acquiring only 100 to 300 MB of data. At room temperature, however, sampling even at 20 kHz will fill 1 GB of storage. If you can reduce your sampling needs at lower temperatures, the battery should be sufficient to acquire 1 GB of data.
What does 1 GB mean in terms of recording life?: It depends on your sample rate and your duty cycle. 1 GB will allow acquisition of approximately 500 million acoustic samples. Divide 500,000,000 by your sample rate in hertz and that will be the total "on" time in seconds. For example, at a 2 kHz sample rate the 1-GB storage will last 250,000 s or about 69 hours. If you sample according to a duty cycle you will of course have to expand the total deployment life by the "off" time between sampling windows.
There are horror stories about batteries dying too soon.: Battery performance can vary dramatically from manufacturer to manufacturer and even from batch to batch. Manufacturer's specifications are no assurance that a given cell will perform adequately. For this reason it is impossible to guarantee the B-Probe's recording life. Always test batteries from a new batch before heading out to the field. Also, dirty or tarnished battery connections substantially reduce battery lifetimes! Be sure to clean the Probe's battery contacts regularly, and to clean the contacts on the battery itself before use. A contact enhancer such as Stabilant 22 may help; in August 2005 Stabilant 22 was applied to the battery contacts of six Bioacoustic Probes deployed on northern fur seals in the Bering Sea, and all six recorders filled their storage units. For more information, download the manual and check the troubleshooting section.
Why can't the B-Probe use movement- or solar-based power, instead of a battery?: Self-powering systems, such as self-winding watches and solar-powered calculators, run on power levels measured in microwatts. At present the B-Probe typically requires between 20 and 30 milliwatts when sampling, far more than a movement- or solar-based power system could provide.
Why doesn't the B-Probe use a rechargeable battery?: A rechargeable battery could be encapsulated in resin, instead of requiring a protective pressure housing to allow field replacement. As a result, the B-Probe would be smaller, more robust, and simpler to operate. Unfortunately, rechargeable batteries cannot be counted on not to "outgas" during recharging. Even a small amount of released gas trapped inside the resin could deform the Probe and, in extreme cases, create a hazardous situation.
I don't like your name for the instrument. Can you call it something else?: Yes, this is indeed a frequently-asked question. The name evolved from space science, a field where the word "probe" connotes small but powerful autonomous packages capable of gathering data where human beings cannot. The typical user for the Bioacoustic Probe, however, works in the biological sciences. We are considering alternative names.
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The Bioacoustic Probe

Frequently Asked Questions