Thanks David and Raimund for the suggestions and advice. I've been away
doing some more field work, hence the tardy reply. But it also gave me a
chance to try some of your suggestions.
I tried coincident (XY) arrays at a few different angles, also a single omn=
(Sennheiser ME62), and compared with the ORTF array I've been using. I thin=
that for my purposes, I'm still going to stick to the ORTF array. I'm _not_
trying to sum the two channels (hence avoiding the potential mono problems)=
I'm analysing them separately, using an averaged power spectrum for each
channel in Raven. The ORTF array seems to give me a wide soundfield to deal
with the extremely wide area I have, and in circumstances where I have
distinct difference between left and right in the soundfield (in one
example, I have a railway line to the extreme left of my soundfield) it
discriminates nicely between the two sides to allow me to compare. It also,
for my money, produces a realistic sound on the equipment I have (Monitor
speakers - Fostex PMO-4's) plugged into the PC.
I don't pretend that this setup is ideal (or even good) for anything else,
but it seems to work best for what I am trying to do with it. I haven't
tried an MS rig because, frankly, at the moment I don't have the money to
I think I will try and battle my way through the file system and put up som=
pictures and a couple of sound grabs. If you haven't actually experienced a
flying-fox camp you probably have no idea of some of the challenges I'm
trying to deal with. But I will admit that in spite of being difficult, it'=
a hell of a lot of fun!
On Behalf Of animalsounds
Sent: Thursday, 16 June 2011 2:42 AM
Subject: [Nature Recordists] Re: Introduction...
> b) allows me to get an averaged
> sound level and frequency distribution spectrum for the 10 minute duratio=
> of the recording (using Raven 1.4); and
I would perhaps recommend to use single (calibrated) omni-directional
microphone for this kind of analysis. As David already pointed out, summing
up the two stereo channels of an ORTF array could lead to odd effects.
> The shotgun mics I have access too (Sennheiser ME66 and ME67) do not seem
> be able to abstract to this extent. Maybe a better mic
> may achieve this but sadly at the moment it's out of my league.#
No, for your particular application, the more expensive MKH series shotgun
microphones will not provide any advantage because the pick-up patterns of
all these models are quite similar. Actually, the MHK series microphones
exhibit a higher noise level at frequencies above about 10 kHz, which could
be a problem for your spectrographic analysis.
> I must admit to being a little worried about the frequent comments I come
> across in various areas of the scientific literature regarding supposed
> "colouration" of the sound by the parabola? Although both reviewing
> on this list, and doing a little research of my own into the published
> literature, this does not seem to be a huge problem providing you are
> concerned with on-axis recordings of above the critical frequency for the
> dish diameter you are using. Or have I missed the point entirely
Yes, you are right. There will be some coloration caused by the parabola,
but as you explained, there are no alternatives under these specific
circumstances. Even a recording made with a shotgun microphone can be
affected by coloration effects as soon as there are reflections off the
ground or nearby vegetation.
> If I understand things correctly, there's no necessarily perfectly correc=
> answer for anything in this game; like in many fields, the answer is
> "it depends."