Friday, March 14, 2008

What mics are good for recording quiet subjects & spaces?

Budhaditya wrote on the Phonography list:
"I would like to hear from you abou
t the critical choice of microphone in field recording, specifically for capturing quieter sounds..."

I can get you started on researching this question. The rule of thumb for recording subtle sounds and ambience in quiet locations is to use mics with no more than 16dB(A) self-noise. Here's a list [htm] of suitable mics that I compiled and is reasonably complete. (Other lists)

Your Soundman OKM II K binaural mics "spec" with 32 dB(A) "self-noise" which is better suited for recording in loud enviroments and louder effects. Used In quiet places where the gain has to be increased considerably, the mics' self-noise will contribute audible hiss regardless of the recorder used. Should you be happy with the Soundman mics, you can consider buying a less expensive recorder because the high self-noise will always "mask" or cover-up the very low-noise performance of the mic preamps in the Fostex FR2-LE and Sound Devices 700 recorders. You Sennheiser MKH-416 mic requires phantom powering though which these two recorders provide. Your MKH-416, with 13dB(A) self noise, should be a lot quieter than the Soundman mics.

Your Soundman OKM II mics may require what is called "Power In Plug" or "PIP" in which the sound recorder supplies the DC voltage to run the mics through the 3.5mm stereo mic input jack. The Fostex or SD recorders don't have this input. Their XLR type connectors supply 24/48 volts phantom for condenser mics. You can buy or build an power adapter to run the Soundman mics on a SD or Fostex recorder.

Nature recordists tend to do ambient or "diffuse field" recording pretty regularly and the largest group/Listserv of such recordists has an archive with a lot of relevant discussion you can search & read.
http://bioacoustics.cse.unsw.edu.au/archives/html/naturerecordists/

To save you some reading time, below are some searches, by model number, of omni-directional mics that are frequently discussed on the list:

Phantom-powered, omni-directional mics for recording ambience in quiet places:
Audio Technica "AT-3032" Inexpensive. Surprisingly, low self-noise.
Senheiser "MKH-20" popular, expensive mic. Newer model is MKH-8020
Senheiser "MKH-800" Popular more expensive, multi-pattern mic.
Rode "NT2000" mid-priced, multi-pattern mic. Heavy.
Senheiser "MKH-30" Expensive. Used primarily as the "side" mic in "MS Pairs"

For small mics with a litle less self-noise, the Shure "WL183" [23dB(A)] and the Danish Pro Audio DPA 4060 [23dB(A)] are popular. The DPA mics are small enough to fit inside of the ears. For small mics with sunstantially less self-noise,~14dB(A), the Telinga "EM-23" or "EMKS-23" mics can be made in a fairly small package for PIP. Klas Strandberg ,who is currently the only source for this EM-23 configuration, might have to be coaxed into making them and they are not cheap. As the Primo EM-23 capsules can be purchasd (sans FET) for $60 each, folks on the MicBuilders list are currently trying FET options to achieve similar results. Here's a comparison test with some of the popluar small, electret mics people are using. If you are curious, the self-noise of your Soundman mics "spec" similar to that of the WM-61A's in the test.

Searching the models terms I put in quotes will get you started. Another very important factor is the "stereo"array" used and also shock-mounting and wind-protection. Curt Olson's simple to make wooden Stereo Mic Rigs are certainly worth a look and listen. Walt Knapp has some good photos of popular MS pairs using Sennheiser mics. Rob D.

15 Comments:

At 3:59 PM, Blogger budhaditya said...

I consulted your write-up more than once, but never thought of posting a comment. Here is my gratitude for initiating me into microphonism.

Thank you.

Budhaditya

 
At 9:05 PM, Blogger Rob D. said...

Glad to help, budhaditya. Let us know how your mics work out for you. Rob D.

 
At 10:11 AM, Blogger BurrenYoga said...

Hi Rob,
Really appreciate your spreadsheet with info on self noise, sensitivity and pattern type.

The most comprehensive i have ever seen!

Thank you.

I am looking for a Lavaliere mic which has very low self noise to record quiet sounds in a very quiet - silent environment.

I am going to click on each mic in your list to try to see which ones are Lavs.

If you could point me in the right direction i would appreciate it.

Sound Professionals have pointed me to the AT943-SP which i think is the same as the ES943 in your list. You specify 29 db which does not sound so quiet.

Hmmmm i am supposed to order these tomorrow.

Best Wishes,
Dave

 
At 11:07 AM, Blogger Rob D. said...

Hi Dave--
Right, 29 dB(A) is not at all "quiet," unless you are recording in loud environents or robust music.

Unfortunately, all but a very few mics with under 16dB(A) self-noise utilize 3/8" or larger diameter capsules. To get the best results in very quiet locations, mics with under 10 dB(A) self-noise will perform sunstantially better. For small size and low self-noise, the best commercially available compromise I know of is the Telinga EM-23's. Plug "em23" into the natrec list archive for a great deal of info on these mics. They are pretty pricey and delivery time is considerable. The next best compromise are the Shure WL-183's which are on par in terms of self-noise with the more widely known DPA 4060's (at a fraction of the cost. WL-183: http://www.uwm.edu/~type/audio-reports/Shure-WL183s/index.htm But again, if you are after minimum hiss in quiet locations, there is no substitute for mics with under 10dB(A) self-noise. Most of these are much larger mics. Wish I had a different answer for you. Let us know what you come up with. Rob D.

 
At 11:31 AM, Blogger BurrenYoga said...

Hi Rob,
thank you for your prompt reply.

Size is not too critical for me. I need to be able to attach it to somebody's t-shirt and record poetry in a very quiet environment. That is the main use i will use it for. I am hoping to capture the full sounding voice, including the sebsuality and naturalness of the voice. The person will not be used to wearing a mic, and may move their head from side to side.

It's ok if the mic is seen, but ideally shold be comfortable to wear attached to a t-shirt.

I am guessing that a mic capsule of 3/8 inch could still produce a reasonably small mic. Do you know of spefic ones with low noise and would be quite small and able to attach to a t-shirt.

I might be able to stretch my budget to the mic Telinga EM-23.
Sounds excellent from what i have read in past 5 mins.

I will be plugging it into a Sony MZ-RH1 minidisc, so the 1/8 inch plug also appealing.

I have put the order 'on hold' until i find out more.

I will check out all your pointers from your previous reply, and if you have any more given that i could 'relax on the size', that would be appreciated.

Best Wishes,
Dave

 
At 6:02 PM, Blogger Rob D. said...

Hi Dave--
Though the background room sounds may seem "quiet," the sound levels of the person reading poetry will be much louder in comparison. If the mic(s) are placed on the performer's shirt about 9" from the speakers mouth, this is considered a robust sound source and the recorder's "gain" may be set low. In this case, the self-noise of the mic is not amplified like it would be if you were recording a quiet place or sound and thus the self-noise performance of the mic becomes dramatically less critical. Even the noise generated by mics with a self-noise rating of 29dB(A) would be inaudible "against" the much more robust sound level of the speaker's voice.

Therefore, the small, omni-directional, lavaliere mics designed for this purpose are a good match-- including those available through Sound Professionals.

With the RH-1 recorder, you might want to use the "Lo Sens" setting for voice to reduce the possibility of over-modulation.

Be sure to tell the sales person you are buying the mics for the Rh-1 as they might be able to better match the mic's PIP voltage requirement.

If you are going to record other subjects over time, I suggest buying a stereo pair which will cost only a little more and will increase your enjoyment.

"Quiet" can be a subjective experience or an actual, extremely low sound level. I took your description literally and made the question more complicated than it needs to be. Rob D.

 
At 11:24 AM, Blogger BurrenYoga said...

Hi Rob,
The poetry that i will be recording has long pauses of silence, and that is when the noise is very noticable.

For most normal speech i think a self noise of 29bD may be ok (while the person is speaking).

After much more reading of this forum, and your previous reply i am leaning towards a stereo pair of Shure WL183's wired to use PIP with the MZ-RH1

I am a bit puzzled about the WL93's i saw compared to the 193's... but apparently no definitive outcome posted on the comparisons made?

Best Wishes,
Dave

 
At 3:24 PM, Blogger Rob D. said...

Hi Dave--
No publicized report on the 193's but they did test noisier than the 183's --possibly because of the way the capsule achieves the cardioid polar pattern. I'd go with omni 183's for lavaliere style micing and general use. The key to low noise is short mic to mouth distance (~9"). With omni mic(s), head movements will create less variation in volume and tone in the recording. This is a blessing should you ever want to edit the material. Rob D.

 
At 3:28 PM, Blogger Rob D. said...

As per increased noise during the performance pauses, use the manual gain setting on the RH-1 recorder. Manual gain doesn't produce the volume "pumping" and other agitations that are produced by the auto gain setting. With manual gain, the background level should remain the same as when the performer is speaking. Rob D.

 
At 5:50 AM, Blogger BurrenYoga said...

Thanks for all the advice.

I bought the AT943's 2 omnis wired as dual mono into a mini plug suitable for the MZ-RH1

The big mistake i made in the past, was that i was using Auto Gain, so in the silent pauses, the mini disc was highering the gain which introduced hiss.

I am now using manual recording levels, no auto gain, and mics very close to mouth (5 inches using a headset) and the AT943's are working very good in this setup.

I am experimenting with mic sensitivity high and low, to see if adjusting this setting will help minimise background noise.

The worst noise i am experiencing in my recording situation, is when some is coughing in the audience.

I have tried using one cardioid element and one omni (the AT943's have interchangable elements) but even with the cardioid the coughing is quite loud and i don't have the skills to remove it using Adobe Audition.

But at least my initial goal of have reasonably silent recording during the pauses has been achieved.

Best Wishes,
Dave

 
At 1:17 PM, Blogger Rob D. said...

I'd use the "Hi Sens" setting on the Hi-MD unless close-micing-- closer than ~2 feet away unless you are projecting your voice loud.

"Silence"during playback is a function of foreground/background ratio and overall speaker playback level. When recording, more distant micing is more atmospheric with less contrast betweene foreground and background. The background will be more audible upon playback than close-micing.

You seem to be trying to work out the best balance between sounds in your studio you want to hear in the background and those you do not. Mic placement is key. After you find the "right" place(s) to mic from, the next steps are treating room acoustics and editing. Rob D

 
At 4:08 AM, Blogger BurrenYoga said...

Thanks Rob,
I am positioning the microphone AT943 lavaliere omni 5 inches from my mouth on a headset.

It is able to pick up the cough from a person in the class who is 10 feet away.

I tried using a cardioid, but this also picks up the cough.

Any tips on what i could do to shield the mic from the cough, or absorb the sound?

The walls have little or no soft covering or furnishing. It is essentially an empty room with floor boards, large windows (these have full length curtains), walls made of plasterboard.

I have the Mini Disc set to high sensitivity, and record level down to 10.

The goalposts keep moving with this 'Art' of recording ;-)

Dave

 
At 9:53 AM, Blogger Rob D. said...

Oh, I thought you were trying to record ambience. A lavaliere mic 5" from your mouth is classic, "close-micing," isn't it?! For this type of micing, DO use the "Lo Sens" setting. Using lower gain this way may help with higher than usual background sounds-- especially if your voice was over-recording and sounded distorted on "Hi Sens."

I know of no way to remove a cough in the background of a recording except to edit it out. Filtering won't do much. Rob D.

 
At 10:00 AM, Blogger Sheena said...

oh thanks for this but i think filtering wont do much!

 
At 1:44 AM, Blogger Jenis Broad said...

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