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Digging Deep: Getting the Most from Your Audio Data

by Steve Moon



I have collected and analyzed audio data for more than a dozen years. Collecting and analyzing audio is, I believe, one of the better research tools for relict hominid research. And the secret to effective audio research is getting the recorder out and putting it to use, and taking the time to analyze the data.


Relict hominid research utilizing audio recording generally takes two very different approaches. I call them trolling and digging deep. Trolling allows you to sample a broad geographic area. Digging deep gives you the ability to zero in and discover nuanced behavior in a population once it is known in a specific locality. Diving deep usually follows trolling, and often the two are combined in a research design. Your research needs and style will determine your individual approach. You will most likely find it necessary to employ both.


Sound files are easily shared, but finding a receptive audience and receiving feedback is never an easy task. The research that I do is largely for an audience that I anticipate will exist at some time in the future. To that end, I’m assembling a collection of sound files that are organized by date and place so that my data is easily accessible. These audio files are accompanied by photos of the landscapes that my audio files describe as soundscapes, written transcripts, sound clips and sonogram images. Currently just short of five thousand files and approaching one and a half terabytes in size, the collection is archived on three four terabyte external hard drives that are kept isolated from exposure to the Internet. These are updated with new drives every couple of years or as needed. One of these drives is stored remotely in case of catastrophic loss of the other two.


Taking it All In


Taking in all of the fine nuances of a field recording isn’t an easy thing to do. A huge barrier for the intended audience tends to be a lack of proper equipment and technique for listening. Let’s do a deep dive into how best to listen to sound files.


There are two barriers to effective listening; personal limitations and technical limitations. Personal limitations involve things like hearing disabilities, lack of disposable cash, lack of free time, and lack of motivation, to name a few. I’m pushing seventy years of age, and my hearing used to be a lot better. I’m constantly hearing a field full of crickets and cicadas accompanied by a high frequency ringing sound! However, when I put on a pair of headphones or crank my sound files through a good set of speakers, pretty much all that I hear are the sounds that I’ve recorded. It has always been the case that I hear more in my audio files than I do when I’m in the field. Part of that has to do with how sensitive my recording equipment is, but a lot of it has to do with how I listen to my sound files.


Technical limitations can be boiled down to a few pieces of electronic equipment. Let’s look at the equipment side of things, because as a researcher you will need these tools in order to gain the most from your field recordings. The better you can hear what’s going on in a soundscape, the livelier it will be, and the more you will learn from it. The whole process will become more enjoyable as a result. And honestly, if you’re motivated, disposable cash isn’t that much of a barrier because none of the equipment is prohibitively expensive.


Amplifiers


Sound files need amplification. Personal devices such as iPhones and computers have built in or ‘on-board’ amplifiers, but these tend to be woefully inadequate. Even high end gaming sound boards in personal computers won’t do as well as a standalone amplifier when it comes to reproducing sound faithfully. Many of these amps favor lower frequencies, and none are designed to reproduce a broad frequency range without some compromises. Home stereo systems do a much better job. If you have a home stereo system you probably own a tube or solid state (non-tube) amplifier. Tube amps have a characteristic warmth that makes music sound truly wonderful, but solid state amps are much better in terms of acutance; their sound is more detailed.


Field recordings are almost always two channel stereo recordings. Home stereo system amplifiers are two channel, or in the case of home theater and surround sound systems, five channel, seven channel, eleven channel, and so on. A dedicated solid state two channel stereo amplifier is the best choice for amplifying field recordings. As the saying goes, “everything you need and nothin’ you don’t!” When it comes to home stereo amplifiers newer tends to be better. But a decades old stereo amp will usually do a fine job. I own an Emotiva solid state BasX stereo amplifier, made in Tennessee, and it does an amazing job. The latest version of this great little amp (BasX A2m) can be had for less than $300. Yamaha makes a very nice solid state two channel stereo amp (R-S202) that can be had for less than $200, and it sounds great. I own one of these as well, and I highly recommend them both. Any standalone amp, whether two channel or multi-channel, will be superior to the amp in a personal device or computer. The more channels an amp has the higher the cost, which is another reason for going with a two channel stereo amp.


Newer two channel stereo amps tend not to have equalizer circuits. This is a good thing. An equalizer is unnecessary, particularly for field recordings, where the desired result is faithful reproduction of what has been captured. An equalizer allows you to emphasize certain parts of the overall frequency range, usually to compensate for inadequacies in the listening space when using speakers. This is totally unnecessary when using headphones, which you will want to use for listening to field recordings.


Digital to Analog Converters


Digital to analog converters, or DACs, convert a digital sound file to an analog signal for amplification. Typically these utilize a USB cord to transport the digital sound file from a personal device or computer to the DAC, and a pair of RCA cables to take the analog signal from the DAC to the amplifier. A DAC can be a large unit costing thousands of dollars, but some very adequate and good sounding DACs can be had for around $100. One of the very best of the more affordable DACs is the MODI ($129) by Schiit Audio. Schiit Audio is a southern California company that specializes in well-made high end stereo equipment at reasonable prices. I recommend no other. These are stellar sounding units! DACs are built into personal devices and computers as part of the onboard amp, but just as the onboard amps are not so hot, neither are the onboard DACs.


Switch Box


Assuming that you will also be using your stereo amplifier to listen to other sources such as a CD player or Bluetooth antenna (Emotiva has a Bluetooth antenna (BTR-1) priced at $80), you will want a stand-alone switch box. These are typically around $30, and are a simple device with a passive copper circuit and no processing components. The DAC and switch box are both small unobtrusive units, and are available in silver or black to match your home stereo components.


Headphones


The final stage when listening to nature recordings is the headphone. There is a huge variety in headphones. Some provide a sound response that is ‘flat’ meaning that all parts of the frequency range are treated equally. This is what we want. Many headphones emphasize base frequencies, usually at the expense of some other part of the frequency range. Our goal is to hear the sounds of nature as faithfully as possible, so hearing all parts of the sound spectrum equally well is important. Surprisingly, more expensive headphones are not necessarily better. My favorite is the AURIANA Live!2 by Creative. These are usually available for about $70. They are a ‘closed’ rather than ‘open’ design, meaning that they fit over and enclose the ear, making it easier to concentrate on your recordings without the distraction of sounds that are around you. Some headphones are ‘noise canceling’, meaning that they electronically block out surrounding sounds, but this entails added circuits and I don’t recommend them. Again, less is more. But if you don’t have a quiet place to do your listening, a pair of noise canceling headphones is the way to go.


Ear buds can be used and are not a bad option. Unlike headphones, you generally have to spend more for better quality ear buds. Bose, Sennheiser, Apple, and many other manufacturers produce quality ear buds which reproduce sounds well throughout the spectrum. Like headphones, some ear buds are designed to be base-heavy. That is not a good thing, because again, when one part of the frequency range is emphasized it’s at the expense of another. We’re looking for a faithful, natural sound response. Because high quality ear buds are not available at a reasonable price (to the best of my knowledge) I can’t recommend them for the analysis of sound files recorded in nature. If you have a pair, and especially if you have a high quality pair, by all means use them!


A Summary of the Listening Chain


At a bare minimum: ear buds or headphones plugged into your personal device or computer. (iPhone/computer-headphones/ear buds) This isn’t optimal, but it’s better than trying to listen without headphones or ear buds.


For a better listening experience: reasonably good quality headphones plugged into a solid state amplifier, with the sound file fed to the amplifier from your personal computer or device via a digital to analog converter (DAC). (computer -> DAC -> amplifier -> headphones)


For Further Consideration


Whenever I purchase audio cables, patch cords or related items, I shop around for the best deal I can find on high quality items from a supplier like Blue Jeans Cable or Audio Advisor. Your sound system is only as good as its weakest link. If you plug your headphones into an amplifier using the most inexpensive adapter you can find, the signal you ultimately listen to will be compromised. The adapter I use for this purpose cost around $30, and I consider that a good investment.


The room that you sit in and your comfort level are but two of the many conditions that will affect your listening ability. The time of day will also have an immense impact on how well you are able to listen to sound files. Listening in the morning is usually better than later in the day. Your mood has a huge impact as well. Caffeine, sugar, alcohol, THC, and any other drugs that you partake in will affect your listening ability. Be sensible with your use of any of these and try to be aware of the changes to your cognitive abilities that they cause. Acknowledge impaired ability when it becomes apparent to you, and adjust your listening habits accordingly.


Sound files recorded for field research tend to have a high ‘noise’ level, meaning that there is typically a hiss or high frequency sound present that can be uncomfortable or even harmful to your hearing. Insects and amphibians also make piercing high frequency sounds. These can all be filtered out or minimized in a sound file by using a ‘low pass’ filter in a program such as Audacity (a free download) or Adobe Audition. Low rumbling noises from wind and other sources can similarly be filtered out using a ‘high pass’ filter. It is often very necessary to do this in order to hear the faint sounds that digging deep requires, because you will want to listen at an elevated sound level. Crank it, but protect your ears. When listening to a sound file always work with a copy of the original file, not the original.


Whatever equipment and technique you use to listen to your sound files or those of colleagues, “practice ma’am, practice!” You will definitely benefit from regular listening sessions. The act of listening is the only way that you will gain insight into the bioacoustics of relict hominids.


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