## How to capture very low volume sounds?

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A while ago I was surfing some nerdy geeky website and found that a company had designed that mic that could capture really low volume sounds like the sound emitted by the filaments of a light bulb for example. I cannot find that page again but how do you guys would go about recording sounds that no-one can ear? piezo mic? what techniques?

thanks!

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I'm a +1 on the contact mics. If there's something too quiet for me to be able to record with a conventional mic (which is because I don't have access to an anechoic chamber...) I usually grab a contact mic. It's basically the equivalent of putting your ear directly on something, and then some...

One of the biggest challenges to recording quiet sounds is Medium Transfer. As sounds transfer from medium to medium (such as a gas to a solid, or a liquid to a gas), you lose SPL. Let's say you're trying to record a lightbulb filament. The sound has to transfer from the filament to the gas in the bulb, then transfers from the gas to the glass bulb, then transfers from the glass to the air around it, then to the microphone element. That's 4 transfers between a solid and a gas, hence a lot of lost SPL. If you take 2 transfers out of the equation by attaching a contact mic directly to the glass, you have a lot more SPL to work with, and therefore can get a much better signal to noise ratio.

Now obviously you can't always attach a contact mic to a specific surface, but usually you can find a way to. I've been playing with the one I just made a lot lately. Lots of fun! You can make one from parts from radio shack for under $8 (as long as you already own a soldering kit) Just wondering if it is appropriate to talk about SPL when refering to contact mics. As SPL is a measurement of absolute sound pressure at a defined distance from the source. (with contact mics there is no atmosphere or distance involved).. – Eric Baca – 2011-12-03T20:40:24.793 7 Sanken make a contact mic that can record ants footsteps or termite activity but it costs US$3000... From their website- In 1999, very special contact mic, called “Insect Mic” (MO-64) was introduced. It can pick up sound of ants’ footsteps or heart beat of snail.

3http://www.bbc.co.uk/radio4/science/thematerialworld_20031120.shtml An interesting radio show on new technology that can capture the sounds the cells in our body make. Obviously a little extreme in relation to this topic, but interesting nonetheless! – Lachlan Harris – 2010-03-13T02:58:39.047

1I want one... \$3000 though? Yeesh! – John Keston – 2010-03-09T20:02:22.787

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Equipment wise, I have three approaches for very quiet sound sources: Contact mics (picking up mechanical vibrations rather than air), a large condenser mic (inherently lower self-noise than small condensers), and Sennheiser MKH mics (lowest noise mics I can afford).

Technique-wise, more than half of it's listening. When I hear tiny, delicate sounds, I grab them, regardless of what makes them, because really subtle sounds can be used for many different things. Fluorescent lights that produce a rolling series of clicks as they're turned on are my favorites.

Selcuk provides really important advice, though: Sound design is a mix of capturing, editing, and recontextualization. Making it sound right doesn't mean making it sound accurate. This also takes the pressure off of trying to record the impossible.

Georgi is also painfully correct: Rooms, and even what's outside those rooms, starts to matter a whole lot once the sound source gets super quiet. Can't tell you how much I cringe when I can hear exterior noise in the backgrounds of what I record indoors. :-(

All this said, there are scientific devices and techniques that record infrasound and ultrasound, but the recordists I know don't have access to such gear.

Just wanted to point out that air and solid propagation of sound are both of a mechanical nature. – Eric Baca – 2011-12-03T20:25:40.240

Weird to add a comment to my own post, but here's a pretty definitive set of ultrasonic recording gear from Germany, with loads of audio samples. http://www.avisoft.com/

– NoiseJockey – 2010-03-31T15:34:32.867

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An easy way to a solve the problem of outside noises in your room while recording something quiet -- try doing it in the middle of the night. At 12-5am there usually no traffic, yelling, walking, etc.

That entirely depends on where you live. I have lived in several places where the activity outside never stops.

Right now I am lucky in that matter, as I have access to more anechoic, sound proof rooms than I have fingers :) – EMV – 2010-04-22T16:59:28.063

at 5am there are typically enough birds vocalising outside to ruin anything quiet.. – georgi – 2010-04-23T01:18:20.207

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That's a good question. I guess contact mics would be a good option. Check out this question for some info on contact mics. If the sound is so low that one can't record it without a lot of noise, I'd probably just try design it from scratch using alternative and louder materials .

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then there are a few very quiet microphones.. but they require quiet rooms..

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Hi guys,

Thanks for all your answers! :) I found a guy that builds its own contact mics, they seem rugged enought to be plunged into some soda water so that sort of mics would be interesting I guess to capture very quiet sounds or sounds you find in unusual environments. here is the link: http://www.getlofi.com/?page_id=1479

Watch the video, pretty cool

@Selcuk Can Guven

By sounds you cannot ear I'm talking about their volume being so quiet that you cannot ear them, or sounds that exist in environments that sound technology don't have access to (yet) not sounds that fall out of the human earring range in which case yes it would be absurd to try. Check that cool Nasa link:http://www.nasa.gov/vision/universe/features/halloween_sounds.html That's just to illustrate that sounds that you cannot ear can indeed be captured and played back.

I'm still trying to find that link about those guys that invented that suction mic I'm talking about above but with no luck...

1Cool, the last example on that NASA webpage contains the source sound for the 'distress signal' in the 2007 movie Sunshine. I watched that movie last saturday and recognised the sound immediately when listening to the Nasa snippets. – EMV – 2010-04-21T06:20:38.270

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I once knew an engineer who had to go record insects overseas. He had custom microphones created for him from a very reputable pro mic company in order to capture the ever so quiet sounds of the insects he was documenting. Hope that helps

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You may find some answers from the scientific community, especially those folks working wildlife. Just this morning I watched a program about elephants and the different ways they communicate with each other. Scientists have discovered that the elephants use subsonic frequencies to send signals over long distances, covering more than 110 sq. miles::

http://www.elephanttag.org/Professional/professional_elephant%20vocalizations%20and%20behavior.html

Similarly, researchers have discovered that trees "sing". Using specialty microphones (similar to hydrophones, I think) and recording at insanely high sample rates, they can hear the trees "vocalizing" as the weather changes:

http://emusician.com/daw/emusic_going_wild/

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I'm late to the party, but just wanted to add: Rode makes a very cheap and super quiet LDC mic - the Nt1a. Self noise is -5.5dB-A, and costs £144 including popshield and suspension. It also has good sensitivity, 25mV/Pa, all in all great specs for capturing really delicate stuff for when a contact mic is not the best or convenient way to go.

Of course, you still need a quiet room... and not just treated in terms of basstrapping etc, but this mic is so sensitive/quiet that when I make recordings in my room, it picks up the street booming along - whilst I can't hear the street myself just with my ears. Which means I often have to grab some absorption panels and set myself up in the hallway to be away from that noise.

Even though this is a studio mic, apparently it works well in exterior situations too. The people on the nature recordist yahoo group have been experimenting with this, with apparently great results.

All in all, especially for the price, an amazing mic!

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Some great suggestions up thread. I'd simply add induction coil microphones. Cheap, interesting. Can get inside objects in ways that contact mics don't.

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I had my zoom perched on the desk unknowingly right against my porta hard drive and monitor was enabled and i was able to pick up a really nice hard drive hum coming from it so I then decided to record that and went on to establish a recording for my Macbook Pro.

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I should also mention, most of the very "quiet" sounds you hear on nature programs (like ants footsteps, insect wings ect) are not the actual sounds being emitted by the "source" seen by the camera. Most of these sounds are created by Foley artists in a studio with household items!