What is Microphone Attenuation? - ehMac.ca
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Old Sep 11th, 2009, 05:09 PM   #1
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What is Microphone Attenuation?

I recently bought a Canon HF200 and also picked up this microphone. If I plug in the mic and use it with the battery charger connected I hear a really loud buzzing noise. If I turn on Microphone Attenuation the noise seems to go away but my recorded voice is almost too quiet.

What is Microphone Attenuation? and is there any other way I can get rid of the buzzing?
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Old Sep 11th, 2009, 07:53 PM   #2
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Buzzing generally means that the microphone impedance is mismatched - so attenuation suppresses the mismatch noise. The best solution is to have a microphone that is properly matched, a low-Z microphone for low-Z inputs; mid-Z for mid-Z inputs, and hi-Z for hi-Z inputs. Of course, one can use an attenuator or an impedance matching transformer, which will do the job of handling mismatches - but the easiest and best way is to have a properly matched microphone in the first place.
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Old Sep 12th, 2009, 09:18 AM   #3
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It sounds like using the attenuation is causing an effect that appears to solve the problem but in reality it's just an incidental effect.

Attenuation is a lowering of level (in electronic terms) that most consumers would equate with a lowering of volume ... some people might say "it's like a switch that makes the volume go down".

Microphones play a unique role in the recording process, and are capable of putting out a wider range in level (from quietest to loudest sound) than most of the other equipment in the chain.

Because electronics have a more limited ability to handle a range from quiet to loud than the microphone itself, it's possible to for microphone to output a signal that is "too loud" for the electronics to handle.

With solid state electronics (the kind we use in nearly everything now) distortion is very low for most of the range in possible levels, than rises quickly at some point; with digital recording, distortion will go from nearly nothing to 100% at a single point in the level.

The idea is to keep the maximum level you want to record below these distortion thresholds.

The solution is to attenuate the mic output so that the loudest sound the mic outputs is within the range of the electronics themselves.

If you do that, all other aspects, including noise, will appear to go down by a similar amount. However, when you look it as how much wanted sound you have (what I want to record) versus how much unwanted sound (noise) there is, the ratio will be the same when you use an attenuator (unless that unwanted sound is distortion from overloading the electronics or digital recorder; the problem the attenuator is supposed to fix).

In other words, the noise when you play back will be just as loud as before; it will comprise the same portion of the entire recording.

You need to determine the actual cause of the unwanted noise and solve that. If it's overloading the recording electronics then the attenuator will help; if it's something else then using the mic attenuator will only appear to solve it; the problem will actually be there just as much as before when you later go to use the audio you recorded.

I said earlier that mic attenuation is a lowering of level that most consumers equate with a lowering of volume ... hopefully if you understand my explanation you will then also understand that it isn't a lowering of volume but instead just matching equipment levels so they work properly together. Generally in audio "volume" only refers to how loud the playback is.

Evan made a good point regarding impedance; when he says "Hi-Z" that is electronics shorthand for Hi impedance". It's a complex topic we won't go into here, but suffice it to say that most consumers never deal with impedance issues with their equipment ... broadly speaking the manufacturers take care of impedance matching when they design the gear.

However, start using microphones, and now you are the recording engineer and you are in charge of matching the impedance ... not because the industry wants to torture you, but because you are taking on a job that requires an understanding of how recording works.

From your description I would be inclined to suspect ground loop or issues regarding condenser mic power that may be available from the camcorder's mic input connector; perhaps the mic plug is non-standard in dimensions and contacts a power source designed to work with certain kinds of microphone, or doesn't seat properly in the camcorder jack.

However, I must add that from the information provided from the reseller's description for the mic you bought, it's impossible to know if it will work with the Canon, or what, exactly, it will work with. There simply isn't enough information provided to have any idea if it will work or not; most people familiar with recording simply would not have bought it because of that reason alone.

Either be careful to buy only the microphone the manufacturer of your camcorder recommends, because then the manufacturer gets a chance to match the equipment's characteristics so it will work, or get learning.

I'm sure the owner's manual for the camcorder talks about mic selection. This is not an example of a situation where "whatever" will work; if you don't know what you are doing and don't want to spend the time to learn then I suggest you do what Canon suggests you do.

Most people would bite the bullet and get a Canon-recommended mic. Then if it doesn't work, you have a recourse to solve the problem without yourself having to be an expert as well.

Last edited by gordguide; Sep 12th, 2009 at 10:01 AM.
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Old Sep 13th, 2009, 12:10 AM   #4
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I tried plugging the mic into my MacBook Pro to test recording a podcast and the input volume was really quiet. I would practically have to shout into the mike to hear anything on my computer. Is this a settings issue with my computer or is my mike defective?
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Old Sep 13th, 2009, 12:39 AM   #5
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That would be a function of the computer. The audio input is line level not mic level. You would need a microphone pre-amp in order to use the mic in that input.
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Old Sep 16th, 2009, 11:28 AM   #6
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Thanks everyone, a question about shooting modes. On my camera I have MXP FXP XP+ SP LP. These seem to be different data rates. If that is the case should I just film in MXP (24Mbps) all the time?
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Old Oct 6th, 2009, 05:47 PM   #7
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wanted to bump this again to see if anyone can help me with the settings on my camera. Question about Frame Rate on my HF200

On my camera I have 5 different recording modes:
LP - 5 Mbps
SP - 7 Mbps
XP+ - 12 Mbps
FXP - 17 Mbps
MXP - 24 Mbps

Also I have a setting called Frame Rate which has 3 modes:
60i
PF30
PF24

Which combination of settings should I be using? My videos are mainly going to be posted on YouTube so it's not like they need to be super high quality but I would like them to look decent.
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Old Oct 6th, 2009, 07:55 PM   #8
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Perhaps you should experiment - but I think the lower rates will be more than adequate for YouTube. Of course, you could shoot everything at a higher quality rate, then render it down to something more compact for YouTube...
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Old Oct 6th, 2009, 08:35 PM   #9
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Quote:
Higher bit rate rates (e.g. MXP 24Mb/s) have higher picture quality but require the expensive Level 6 flash cards and use them up fast.

This all should be in your manual in more detail.

From Spec Sheet (for Level 6 32GB flash card)

Maximum recording time
LP (5 Mbps) 12 hours 15 minutes
SP (7 Mbps) 9 hours 35 minutes
XP+ (12 Mbps) 5 hours 45 minutes
FXP (17 Mbps) 4 hours 10 minutes - Allows 1920 x 1080 Full HD Recording
MXP (24 Mbps) 2 hours 55 minutes - Allows 1920 x 1080 Full HD Recording
Canon hf200 best shooting modes - Forum - VideoHelp.com
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Old Oct 7th, 2009, 03:12 AM   #10
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Thanks for the link ottoman, very informative. I did do a test shoot with all 5 modes but couldn't really see much of a difference on my MBP.
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