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| About Us |
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| Meeting tight deadlines without compromising on
quality |
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We are digital transcription specialists:
we also transcribe from DVD, CD, VHS, Standard Cassettes
and Micro Cassettes. |
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We produce either verbatim or edited transcripts
of group discussions, depth interviews, workshops and
seminars. |
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Easy client upload facility for digital
recordings direct to our server. |
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McGowan Transcriptions are specialists in
Market Research transcription. Founded in 1993 by Joe
McGowan, we are the leading name for transcription services
in the UK and are appreciated both for our professional
speedy turnarounds and quality of service.
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We are at the forefront of our field and
our secure uploading facility for digital voice files
uses the most up to date technology and security software
available. |
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We have come a long way from transcribing
on typewriters and printing out 1000's of pages per day,
and we are continuously researching the global market
and ensuring our technology is of the highest calibre
in terms of assisting both the client and ourselves. |
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We will always have full facilities to transcribe
from cassettes but envision the future to be purely digital
transcription as the benefits are too many to be ignored. |
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WHY DIGITAL? |
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Audio Quality |
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The recording process used to make analogue
recordings using cassette tape introduces noise, particularly
tape hiss. Noise can drown out softly spoken words and
makes transcription of normal speech difficult and tiring.
Digital recorders generally have a much higher signal
to noise ratio. Less noise reduces the risk of lost data
and results in faster, less expensive and more accurate
transcription. |
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Note that audio quality also depends on
using a suitable external microphone or microphones properly
positioned near speakers in an environment with low levels
of ambient noise. |
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Digital Editing |
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There are cheap, sophisticated audio editing
programs that can be helpful if they are used with care.
These programs can be used to adjust the recording level,
fix recordings in which one speaker sounds louder than
another, reduce unwanted background noise, filter unnecessary
frequencies, silence personal or identifying information
to protect anonymity, and cut extraneous sections from
the beginning or end of audio files. |
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Archiving |
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It is easy and inexpensive to backup and
archive digital audio recordings. When using a compressed
digital format such as MP3 it is possible to store an
entire research project on one or two CD-ROMs. However,
because digital audio is readily copied and transmitted,
additional steps may need to be taken to ensure that original
recordings are kept secure and research participants'
confidentiality is adequately protected. |
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TECHNICAL BACKGROUND |
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Frequency Response |
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The audible range of the human ear is approximately
20 Hz to 20 kHz. The most important frequencies for speech
occur in the "mid range" between 250 Hz and
8 kHz. |
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The sensitivity of microphones and recorders
to audio frequencies varies. Microphones for recording
speech often are most sensitive to the range between 200
Hz and 10 kHz. Digital recorders also vary in their sensitivity.
A MiniDisc recorder, when matched with an appropriate
microphone, is capable of recording frequencies between
20 Hz and 20 kHz. Some digital voice recorders when set
to "long play" mode may only encode frequencies
between 300 Hz and 3 kHz. Telephone line frequencies are
limited to those between 400 Hz and 3.4 kHz. A frequency
response that approximates the mid-range frequencies will
result in the best speech recordings. |
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Channels
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Single channel or mono recording often works
fine for interviews. Mono recording also doubles the available
record time when using a digital recorder. However, stereo
recording may be an advantage in some situations where
the speakers are separated from each other or where there
are several speakers. To take advantage of stereo recording
a microphone setup that allows each microphone element
to be positioned next to a different speaker or set of
speakers will be necessary. |
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Recording Level
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The level of the audio signal-- how much
the microphone signal is amplified-- needs to be set properly
to make a good recording. If the signal is too strong
it will be distorted; too weak and the speech one wishes
to record may be swamped by noise and difficult to hear.
The majority of cheap recording devices do not provide
any visual display of the level and set the recording
level automatically. This makes recording easy but automatic
level control (ALC) can be problematic (Modaff and Modaff
2000). ALC constantly adjusts the level to any audio input,
even background noise during pauses in speech. This may
result in the level being frequently, although briefly,
poorly adjusted to the speech being recorded. ALC also
changes the overall dynamics so that the difference between
loud and quiet speech is compressed. |
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Digital Audio |
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Digital audio is recorded by sampling a
sound wave and assigning each sample a value. The quality
of the audio depends on the sampling frequency and the
resolution, that is, the range of values that can be assigned
to each sample. The sampling frequency is significant
to the extent it needs to be at least double the highest
frequency one wishes to record. Music CDs use a sample
rate of 44.1 kHz -- a rate more than adequate for encoding
frequencies up to 20 kHz. For recording speech, a sample
rate of at least 16 kHz will ensure good quality. Audio
is normally encoded in 8 bits, 16 bits, or in some cases
higher resolutions. The higher the bit depth, the greater
the number of amplitude values that can be represented
for each sample. An 8 bit resolution may be adequate for
recording speech for some purposes, but 16 bits is better. |
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Digital Audio and Compression
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CD quality digital audio corresponds to
a sample rate of 44.1 kHz, encoded at 16 bits, on two
channels. This works out to: |
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44.1k × 16 × 2 = 1411.2 kilobits/second
1411.2k / 8 = 176.4 kilobytes/second
176.4k × 3.6k = 635.04 megabytes/hour |
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To record at this rate consumes a considerable amount
of storage space. The same is true of other forms of
Pulse Code Modulation (PCM) audio, which is the usual
format for Windows WAV files and Macintosh AIFF files.
Even if the encoding rate is reduced by using a 16 kHz
sample rate at eight bit resolution with one channel
(which for many purposes might be satisfactory for recording
speech) the recording will still consume 57.6 MB/hr.
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The solution to the space problem is compression
schemes or codecs that use psychoacoustic principles and
other audio features to reduce the bit rate in ways that
limit the perceived quality loss of the audio stream.
Common compression schemes include: Fraunhofer MPEG 1
Layer 3 (MP3), Advanced Audio Coding (AAC), Adaptive Transform
Acoustic Coding (ATRAC), and Windows Media Audio (WMA).
MiniDisc uses ATRAC, which in standard mode, like CD audio,
samples at 44.1KHz, in stereo, and encodes in 16 bits,
but saves the audio in 1/5 the space without perceptible
loss of quality. Fraunhofer MP3 saves audio in 1/11 the
space. A Fraunhofer MP3 audio file encoded at 32 kbps
(22.05 kHz sample rate, with 16 bit encoding, mono) will
provide good voice recording for many purposes and only
takes up 14.4 MB/hr. Newer codecs such as WMA and AAC
maintain perceived audio quality at even greater compression
ratios. |
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FACTORS TO CONSIDER |
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Cost (including batteries and media if applicable).
It is a false economy to purchase a cheap recorder if
the audio quality is such that it increases the cost and
time of transcription. Transcription is time consuming
so a good recorder costing hundreds of pounds will quickly
pay for itself |
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Audio quality. |
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Easy of use. |
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Microphones. Are external microphones supported
and are they supported through line-in or mic-in jacks?
Internal microphones are usually of low quality, may pick
up noise from the recorder, and may be difficult to position
close to interviewees. An external amplifier, often expensive
and cumbersome, may be needed to boost the microphone
signal to line level if an external microphone can only
be attached through a line-in jack. |
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Portability and intrusiveness in an interview
situation. |
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Ruggedness and reliability of recorder and
media. |
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Audio formats. What type of recording formats
or compression schemes are supported? How easy is it to
use a given format with data analysis, audio editing,
and transcription tools? |
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Stereo recording. Is stereo recording supported? |
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Computer transfer. How easy is it to transfer
recordings to a computer? Is USB or some other method
that allows faster than real time upload supported? |
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Record time. How long will media and batteries
allow recording to continue uninterrupted? |
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Batteries. Can rechargeable batteries be
used? |
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Control over the recording process. Is the
recording level displayed and is it possible to manually
adjust the recording level? See discussion above. |
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Additional information display. Does the
recorder display remaining battery power and remaining
record time? |
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Copy protection. Is a copy protection scheme implemented
and, if so, what limitations does it impose on the use
of audio recordings?
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©2006 McGowan Transcriptions.
All rights reserved
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