Microphones pickup distance

[Kally123]

A question for the sound guys out there.

Does anybody produce a proximity chart for microphones? I am not asking for or about polar patterns, I am looking for a chart that might give affective distances for microphone placement. I do not have a specific application in mind either, I am just wondering if anybody has ever bothered to put that information on paper.

Thanks

 

[MNicolai]

Each model of microphone will have a different pickup pattern, and as polar charts indicate, how much a source is picked up is based on the angle at which the source is from the microphone. I don't even know that such a chart would really even be that useful because each microphone has such a different personality. A lot of it is based on experience, and from operator to operator a lot of personal preference comes into play as well.

For the SM58, Shure does provide a small chart about effective distances that the microphone can be used at.

Check out the bottom of page 5:
http://www.shure.com/stellent/group..._ug/documents/web_resource/us_pro_sm58_ug.pdf

 

[Kally123]

MNicolai

Thanks, I am aware of the information provided from the manufacturers I am looking to see if anybody has put the practical application information on a chart. I doubt that anybody has but wanted to ask.

 

[museav]

It is so dependent upon the environment and application that such a chart would be of limited use. Room acoustics, background noise levels, feedback, mic technique, the level of the talker and so on can all affect the distance one might be able to be from a mic and get a usable or desired signal. Things like whether you want or want to avoid proximity effect can also be a consideration with directional mics. The distance is application rather than just product dependent.

Simple example, would be that a softer spoken person in a very live room with high ambient noise levels and minimal available gain before feedback might require the person to be much closer to the mic than the same mic in a situation with a louder person in an acoustically dead and very quiet room that has the mic well out of the speaker coverage.

 

[rwhealey]

Well, the "pickup distance" is really just another way of talking about gain before feedback.

The Yamaha Sound Reinforcement Handbook has a good section explaining gain before feedback and gives a pretty simple equation to calculate it.

However, as Brad points out, there are many more variables than the simplified equation takes into account.

This is one of those "it depends..." questions that can be quite frustrating

 

[gpforet]

It's no different than speaker output. Sensitivity drops off according to the inverse square law. A doubling of the distance drops off sensitivity by 6 db. Since for all practical purposes, 10 db is considered a doubling of volume or in this case -10 db would be half the output, then for any given microphone, if the output (or sensitivity) is X at 1 foot, the sensitivity will be 1/2 X at approx. 3.3 ft. The problem, like some have pointed out, is that the further the microphone, the more likely to pick up unwanted sound.

A question for the sound guys out there.

Does anybody produce a proximity chart for microphones? I am not asking for or about polar patterns, I am looking for a chart that might give affective distances for microphone placement. I do not have a specific application in mind either, I am just wondering if anybody has ever bothered to put that information on paper.

Thanks

 

[museav]

It's no different than speaker output. Sensitivity drops off according to the inverse square law. A doubling of the distance drops off sensitivity by 6 db. Since for all practical purposes, 10 db is considered a doubling of volume or in this case -10 db would be half the output, then for any given microphone, if the output (or sensitivity) is X at 1 foot, the sensitivity will be 1/2 X at approx. 3.3 ft. The problem, like some have pointed out, is that the further the microphone, the more likely to pick up unwanted sound.

To clarify, sensitivity is a generally fixed aspect of transducers such as mics and speakers that for those electro-acoustic devices defines the conversion between acoustical sound pressure and electrical voltage. Sensitivity is typically defined in mv/Pa for mics and as dBSPL at 1 watt (2.83V into 8 Ohms) and 1 meter for speakers. I think you are actually addressing sound pressure level, which tends to drop with increasing distance from the source, rather than sensitivity.

Also, to be picky a 10dBSPL change is generally considered a doubling or halving of perceived loudness. -10dB is not a halving of the output as noted, -10dBSPL would be about 0.32 times the initial sound pressure level while a halving of sound pressure level would be -6dBSPL. And the problem with using the term 'volume' is that volume is a more generic term for level and I've actually seen people assume that turning the volume control on an amp or stereo from halfway up to all the way up is a 10dB difference since that is doubling the volume. So perceived loudness is a more accurate terminology.

I guess you could say that my sensitivity is high to the volume of errors routinely found in output using of some of the related terminolgy.

 

[gpforet]

You right Brad, I was not inferring that -10 db would be half the voltage, but rather half the sensitivity, i.e. perceived output from from the system. And I do understand your concern regarding the power/voltage/acoustic references. When refering to volume, I always use this term to describe acoustic energy, either from the input side or the output side.

But I think are in agreement that the inverse square law is equally applicable to microphone pickup and speaker output....yes?

To clarify, sensitivity is a generally fixed aspect of transducers such as mics and speakers that for those electro-acoustic devices defines the conversion between acoustical sound pressure and electrical voltage. Sensitivity is typically defined in mv/Pa for mics and as dBSPL at 1 watt (2.83V into 8 Ohms) and 1 meter for speakers. I think you are actually addressing sound pressure level, which tends to drop with increasing distance from the source, rather than sensitivity.

Also, to be picky a 10dBSPL change is generally considered a doubling or halving of perceived loudness. -10dB is not a halving of the output as noted, -10dBSPL would be about 0.32 times the initial sound pressure level while a halving of sound pressure level would be -6dBSPL. And the problem with using the term 'volume' is that volume is a more generic term for level and I've actually seen people assume that turning the volume control on an amp or stereo from halfway up to all the way up is a 10dB difference since that is doubling the volume. So perceived loudness is a more accurate terminology.

I guess you could say that my sensitivity is high to the volume of errors routinely found in output using of some of the related terminolgy.