Thanks for the careful proposal Dan. It would be great for many folks
to be able to participate. Could the procedure be simpler and still
get the data that is most needed? I'd have to be really psych'd up
for the strenuous calibration method you've outlined. For example,
if one knows the exact mics and recorder/recorder level used, a post
test with the gear would probably determine the ambient levels with
as much accuracy as the calibration test. With the larger part of the
non-natural sound energy coming from a distance at under 50Hz,
wouldn't it be very tough to set up relevant field calibration? For
record level instruction, how about something like "...set at -5dB
during a loud, distant event. If a louder event comes, re-adjust the
record level for -5dB (or -10dB, but this is often not marked) and
record for another 30 minutes" Bit depth helps with the accuracy of
the analysis tools I've used and some extra noise is not usually a
concern. I've used the voice method you describe many times in the
city, isn't the dynamic range in the woods too low for this method?
(or is the pollution THAT serious!) I agree that careful note
taking is really important. Having assigned "15 minute" takes on many
occasion, I'd specify at least a half hour. Rob D.
=3D =3D =3D
At 11:56 AM -0700 8/27/05, Dan Dugan wrote:
>Dear friends, this is what we're doing in Muir Woods. Your comments
>will be appreciated.
>
>-Dan Dugan
>
>Recording Protocol for Soundscape Monitoring
>Version 2.0 (Draft)
>
>This is an attempt to set standards for audio recording in
>conjunction with attended soundscape monitoring, so that the work of
>different recordists will be comparable.
>
>Format
> Stereo digital audio.
>
>Microphones
> Type: condensor.
> Frequency response: at least 40Hz to 16KHz
> Equivalent noise: lower than 25 dBA (signal to noise 69 dB or better).
> Effective windscreens are essential. Manufacturer-provided
>foam windscreens are inadequate for outdoor work. Good windscreens
>can be home-made.
> Shockmounts are highly desirable, especially if hand-held.
>
>Stereo Microphone Arrays (listed in the order of preference, best first)
> A: Spaced omnidirectional mics with barrier: Jecklin disc,
>shoulder mounts, head-worn quasi-binaural, lavs tied around a tree.
> B: ORTF array (cardioids spaced 17cm, splayed at 110 degrees).
> C: One-point stereo mic X-Y or M-S.
> Highly directional types like shotgun or parabolic dish are
>not applicable for soundscape recording.
>
>Recorders
> Any digital audio recorder with adequately quiet mic preamps.
>MiniDisc, Compact Flash or hard drive are all good. A record level
>control with steps is a plus. Some kind of scale on the record gain
>control (at least 0-10) is necessary for repeatability.
>
>Recording Level
> To establish a starting point, hold the microphone at arms
>length, sensitive side facing you. Speak normally to a person near
>you. Set the recording gain so that the peaks don't exceed a level of
>-5dB on the recorder's meter. This gain will work for quiet
>environments. Loud sounds will require lower gains.
>
>Calibration
> An affordable scheme for calibrating field recording outfits
>is being sought. Here is one proposal:
> Terminology: "Recording Gain" is the setting of the recorder.
>"Recording Level" is the reading of the recorder's peak meter.
> Equipment: A digital audio workstation with speakers, a sound
>level meter, the recording outfit to be calibrated.
> Procedure:
>1) Prepare a stereo track of pink noise. Make the channels
>uncorrelated if possible.
>2) Filter the track with a high-pass at 200Hz and a low-pass at 2000Hz.
>3) Play the track and read the sound level meter while adjusting the
>monitor level to 65dBA (slow) at a normal listening position
>(measuring position).
>4) Place your mic precisely at the measuring position and adjust the
>recording gain so that the recorder's peak meter reads -5dB (this is
>dBFS, meaning "decibels full-scale").
>5) Note your recorder's gain setting. Use this as a standard gain for
>recording in quiet places.
>6) Make a one-minute recording of this calibration noise. Save it to
>calibrate transfers later.
>
>Slates
> Each take should have a voice announcement (slate) at the
>head or tail including:
> Recordist's name
> Date
> Time
> Location
> Weather and wind conditions
> Microphone(s) model number
> Recorder model number
> Recorder gain setting
> Optional description of the scene and the
>sound sources you can identify, observed wildlife behavior.
>
>Monitoring
> Recording should always be monitored on headphones except
>when doing simultaneous attended logging. Attended logging must be
>done with naked ears.
>
>Delivery
> Make a CD with a track for each monitoring location. Five
>fifteen-minute locations with one-minute slates will just fit on an
>80-minute CDR. Write your name, the date and the time-slot on the
>disc with a list of tracks.
> Tape a Tyvek CD sleeve inside a standard file folder. Write
>the slate and track information on the outside of the folder. Put a
>code number on the folder tab: YYMMDD-T (year-month-day, time slot;
>example 050720-night)
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>
--
Rob Danielson
Film Department
University of Wisconsin-Milwaukee
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