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Tools for Digital Audio Recording in Qualitative Research

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Tools for Digital Audio Recording in Qualitative Research Sociology at Surrey University of Surrey social researchUPDATE • The technology needed to make digital recordings of interviews and meetings for the purpose of qualitative research is described. • The advantages of using digital audio technology are outlined. • The technical background needed to make an informed choice of technology is summarised. • The Update concludes with brief evaluations of the types of audio recorder currently available. Tools for Digital Audio Recording in Qualitative Research Alan Stockdale In a recent book Michael Patton writes, “As a naïveté, can heighten the sense of “being Dr. Stockdaleʼs training is in good hammer is essential to fine carpentry, there”. For discussion of the naturalization cultural anthropology. He is a a good tape recorder is indispensable to of audio recordings in qualitative research, senior research associate at fine fieldwork” (Patton 2002: 380). He see Ashmore and Reed (2000). Education Development Center goes on to cite an example of transcribers in Boston, Massachusetts, at one university who estimated that 20% Why digital? of the tapes given to them “were so badly where he currently serves Audio Quality as an investigator on several recorded as to be impossible to transcribe The recording process used to make genetics education research accurately – or at all.” Surprisingly there analogue recordings using cassette tape is remarkably little discussion of tools and introduces noise, particularly tape hiss. projects funded by the U.S. techniques for recording interviews in the Noise can drown out softly spoken words National Institutes of Health. qualitative research literature (but see, for and makes transcription of normal speech example, Modaff and Modaff 2000). difficult and tiring. Digital recorders This overview discusses the potential generally have a much higher signal to advantages of digital recording and noise ratio. Less noise reduces the risk of provides some technical background and lost data and results in faster, less expensive a checklist of features to consider when and more accurate transcription. buying a digital recorder. It concludes with Note that audio quality also depends on brief comments on the different types of using a suitable external microphone or recorder currently available and the names microphones properly positioned near of some of the leading manufacturers. As speakers in an environment with low levels the technology is changing rapidly and new of ambient noise. recorders are appearing constantly there is little point in recommending particular Digital Editing models as the recommendations would There are cheap, sophisticated audio editing rapidly become obsolete. programs (e.g. Syntrillium’s CoolEdit 2000) Detailed discussion of the methodological that can be helpful if they are used with issues associated with audio recording is care. These programs can be used to adjust beyond the scope of this Update. Let it be the recording level, fix recordings in which noted, however, that audio recording uses one speaker sounds louder than another, ISSUE technology and technique to frame and reduce unwanted background noise, filter structure the representation of an event. unnecessary frequencies, silence personal It is important to keep this in mind given or identifying information to protect that the quality improvement of digital anonymity, and cut extraneous sections 38 technology, when coupled with technical from the beginning or end of audio files. social research UPDATE Archiving Channels It is easy and inexpensive to backup and Single channel or mono recording often archive digital audio recordings. When works fine for interviews. Mono recording using a compressed digital format such as also doubles the available record time when MP3 it is possible to store an entire research using a digital recorder. However, stereo project on one or two CD-ROMs. However, recording may be an advantage in some because digital audio is readily copied and situations where the speakers are separated transmitted, additional steps may need to from each other or where there are several be taken to ensure that original recordings speakers. To take advantage of stereo are kept secure and research participants’ recording a microphone setup that allows confidentiality is adequately protected. each microphone element to be positioned next to a different speaker or set of speakers Computer-based Transcription will be necessary. This will aid transcription Transcription software can greatly improve by making it easier to ensure that a good the usability and usefulness of transcriptions audio recording level is obtained for all (Muhr 2000). This is primarily accomplished speakers and making it possible for the through the automatic insertion of tags that person doing the transcription to use the encode additional data during transcription. stereo separation to help identify speakers See for example DGA’s Transcriber and transcribe overlapping speech. software, which uses eXtended Markup Language (XML) tags. The most obvious Recording Level use of tags is synchronization of transcript The level of the audio signal – how files to their corresponding audio files. much the microphone signal is amplified This facilitates checking, correcting, or later – needs to be set properly to make a good referral as the researcher can go to any point recording. If the signal is too strong it will in the transcript and immediately play the be distorted; too weak and the speech one corresponding segment of audio. Hopefully, wishes to record may be swamped by noise these type of features will be integrated into and difficult to hear. The majority of cheap analysis software eventually. recording devices do not provide any visual display of the level and set the recording Technical background level automatically. This makes recording Frequency Response easy but automatic level control (ALC) The audible range of the human ear is can be problematic (Modaff and Modaff approximately 20 Hz to 20 kHz. The most 2000). ALC constantly adjusts the level to important frequencies for speech occur in any audio input, even background noise the “mid range” between 250 Hz and 8 kHz. during pauses in speech. This may result The sensitivity of microphones and in the level being frequently, although recorders to audio frequencies varies. briefly, poorly adjusted to the speech being Microphones for recording speech often recorded. ALC also changes the overall are most sensitive to the range between 200 dynamics so that the difference between Hz and 10 kHz. Digital recorders also vary in loud and quiet speech is compressed. their sensitivity. A MiniDisc recorder, when Digital Audio matched with an appropriate microphone, is Digital audio is recorded by sampling a capable of recording frequencies between 20 sound wave and assigning each sample a Hz and 20 kHz. Some digital voice recorders value. The quality of the audio depends on when set to “long play” mode may only the sampling frequency and the resolution, encode frequencies between 300 Hz and 3 that is, the range of values that can be kHz. Telephone line frequencies are limited assigned to each sample. The sampling to those between 400 Hz and 3.4 kHz. A frequency is significant to the extent it frequency response that approximates the needs to be at least double the highest mid-range frequencies will result in the best frequency one wishes to record. Music CDs speech recordings. use a sample rate of 44.1 kHz – a rate more social research UPDATE than adequate for encoding frequencies Factors to consider up to 20 kHz. For recording speech, a • Cost (including batteries and media sample rate of at least 16 kHz will ensure if applicable). It is a false economy to good quality. Audio is normally encoded purchase a cheap recorder if the audio in 8 bits, 16 bits, or in some cases higher quality is such that it increases the cost resolutions. The higher the bit depth, the and time of transcription. Transcription is greater the number of amplitude values time consuming and expensive so a good that can be represented for each sample. recorder costing hundreds of pounds will An 8 bit resolution may be adequate for quickly pay for itself. recording speech for some purposes, but • Audio quality. See discussion above. 16 bits is better. • Easy of use. Digital Audio and Compression • Microphones. Are external microphones CD quality digital audio corresponds to a supported and are they supported through sample rate of 44.1 kHz, encoded at 16 bits, line-in or mic-in jacks? Internal microphones on two channels. This works out to: are usually of low quality, may pick up noise 44.1k × 16 × 2 = 1411.2 kilobits/second from the recorder, and may be difficult 1411.2k / 8 = 176.4 kilobytes/second to position close to interviewees. An 176.4k × 3.6k = 635.04 megabytes/hour external amplifier, often expensive and To record at this rate consumes a cumbersome, may be needed to boost the considerable amount of storage space. microphone signal to line level if an external The same is true of other forms of Pulse microphone can only be attached through a Code Modulation (PCM) audio, which is line-in jack. the usual format for Windows WAV files • Portability and intrusiveness in an and Macintosh AIFF files. Even if the interview situation. encoding rate is reduced by using a 16 kHz • Ruggedness and reliability of recorder sample rate at eight bit resolution with one and media. channel (which for many purposes might • Audio formats. What type of recording be satisfactory for recording speech) the formats or compression schemes are recording will still consume 57.6 MB/hr. supported? How easy is it to use a given The solution to the space problem is format with data analysis, audio editing, and compression schemes or codecs that use transcription tools? psychoacoustic principles and other audio • Stereo recording. Is stereo recording features to reduce the bit rate in ways that supported? See discussion above. social research UPDATE is limit the perceived quality loss of the audio distributed without charge on stream.
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