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=
i
(Sennheiser ME62), and compared with the ORTF array I've been using. I thin=
k
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
buy one.
I think I will try and battle my way through the file system and put up som=
e
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'=
s
a hell of a lot of fun!
Cheers.
tim
From:
On Behalf Of animalsounds
Sent: Thursday, 16 June 2011 2:42 AM
To:
Subject: [Nature Recordists] Re: Introduction...
> b) allows me to get an averaged
> sound level and frequency distribution spectrum for the 10 minute duratio=
n
> of the recording (using Raven 1.4); and
Hi Tim,
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
to
> be able to abstract to this extent. Maybe a better mic
(SennheiserMKH8070??)
> 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
postings
> 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
somewhere?
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=
t
> answer for anything in this game; like in many fields, the answer is
usually
> "it depends."
Absolutely!
Cheers,
Raimund
|