[Tweeters] RFI ... recording equipment ..

Guy McWethy lguy_mcw at yahoo.com
Mon Nov 21 11:31:17 PST 2011

 A buddy of mine sent me this link.
Has possibilities ...
Guy McWethy
Renton, WA
mailto: lguy_mcw at yahoo.com

From: Marc Hoffman <tweeters at dartfrogmedia.com>
To: Lyn Topinka <pointers at pacifier.com>; tweeters at u.washington.edu
Sent: Saturday, November 19, 2011 11:28 PM
Subject: Re: [Tweeters] RFI ... recording equipment ..

Hi Lyn,

I listened to your Bewick's Wren recording. Very nice. From that, I inferred that the "background noises" you're talking about are real sounds in the environment (the other type of "background noise" is created by noisy electronic circuitry and low-quality mics and just sounds like "white" noise).

There are three ways to reduce the sound of the background in nature recordings.

1) Get closer to the source. Every time you halve the distance to your subject, its sound is increased four-fold. Meanwhile, the background sounds stay about the same. So the result is that the subject sounds relatively louder.

2) Get a "shotgun" style microphone that picks up sound in a very narrow path directly in front of the mic. Sennheisers are good, popular, and rugged. To use this, you'll need to wear headphones because if you point the mic just a few degrees off-axis, the sound of your subject will diminish radically. Note that shotgun mics don't amplify the sound more than other types of mics, they just reject sound that's "off-axis" from the subject.

3) Get a parabolic dish. This looks like the dish receiver you get for satellite TV, only it's typically made of sturdy but lightweight plastic so you can carry it around. The nature of a parabolic dish is that it takes all the sound that is in front of it and focuses all the sound energy on a "sweet spot" that's inside the dish partly back from the rim. By placing the head of an omnidirectional mic (one with a wide pick-up pattern) right in the sweet spot, you not only filter out sounds behind and to the sides of the dish, but you also get a huge amplification (about 12 dB) of the sound in front of the dish. Again, you need to be wearing headphones to monitor what the dish and mic are picking up. You'll be amazed at the things you hear through the headphones that are inaudible to the unaided ear!

Solution #1 is probably unrealistic, as you're probably already as close as the bird will tolerate.

Solution #2 is less cumbersome than #3 but you might not get a strong enough signal unless you add a microphone preamp. Shotgun mics are around a couple of hundred dollars or more. A good preamp might cost about the same.

Solution #3 is the one I like and would use if I weren't already carrying around way too much camera and lens :)  A good dish costs at least a couple of hundred dollars. I made my own but it took way too much time to be worth the financial savings. You won't need as specialized a mic. Nor will you need the preamp, since you'll be getting lots of signal amplification from the dish.

A good resource for advice and equipment is Oade Brothers (http://www.oade.com/ ). They sell all this stuff and their site has useful recommendations.

We also have a fabulous resource right here in the Seattle area: Martyn Stewart of Naturesound.org.  Martyn has done nature field recordings for BBC and tons of other clients and he is one of the premiere nature recordists in the world. In recent years he has offered a 2-day workshop on sound recording equipment and techniques. You might inquire if he's going to offer that again this year.

Best wishes,

Marc Hoffman
Kirkland, WA

At 10:02 PM 11/19/2011, Lyn Topinka wrote:

hi all ... initially I bought a small hand-held-fits-in-your-pocket digital recorder to take notes with while in the field ... but I ended up using it for bird songs too !!! ... it was fun ... I have the Sony IC Recorder ICD-PX820 ... small, handheld, runs on two AAA batteries ... so, with Christmas now approaching I could ask Santa for something better perhaps ??? ... or a microphone but which one or which type ??? ... any other suggestions which would help eliminate the background noises and just pick up on the birds ??? ...


>if you like this stuff here's what I've gotten so far ...





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