Microphone Sensitivity and Feedback - Revision history

ST: image embedded in text, category added

2009-04-16T17:08:11Z

image embedded in text, category added

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-<noinclude>{{Bose Reviewed}}
+<noinclude>{{Bose Reviewed}}</noinclude>
 It is a common misconception that a microphone that has lower sensitivity (in other words, a sound of a given intensity at the microphone produces a lower electrical signal than a microphone of higher sensitivity) is somehow more susceptible to microphone feedback.
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 Feedback occurs when the sound from the loudspeaker (or loudspeakers if a microphone is connected to more than one) is louder at the microphone than the sound of the voice.
 If you just decrease the microphone sensitivity, the sound from the loudspeaker goes down by the amount of the sensitivity reduction.
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 So it all comes down to one thing:  when there is enough loudness in the room, how much better can the microphone hear the desired source than it hears the sound system? Sensitivity doesn't enter into this equation.

ST: added feedback image (will not be included in other articles) - also made {{Bose Reviewed}} noinclude

2009-04-16T17:06:02Z

added feedback image (will not be included in other articles) - also made {{Bose Reviewed}} noinclude

← Older revision		Revision as of 17:06, 16 April 2009
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	{{Bose Reviewed}}		<noinclude>{{Bose Reviewed}}
			Feedback occurs when the sound from the loudspeaker (or loudspeakers if a microphone is connected to more than one) is louder at the microphone than the sound of the voice.

			This fundamental fact is shown in the figure below.

			[[Image:Feedback fig 1.jpg\|800px\|Microphone Feedback]]
			</noinclude>
	It is a common misconception that a microphone that has lower sensitivity (in other words, a sound of a given intensity at the microphone produces a lower electrical signal than a microphone of higher sensitivity) is somehow more susceptible to microphone feedback.		It is a common misconception that a microphone that has lower sensitivity (in other words, a sound of a given intensity at the microphone produces a lower electrical signal than a microphone of higher sensitivity) is somehow more susceptible to microphone feedback.

ST: Template:Microphone Sensitivity and Feedback moved to Microphone Sensitivity and Feedback: Made this a regular article. It can still be included, but it also might be referred to as an ordinary, standalone article.

2009-04-16T17:03:49Z

Template:Microphone Sensitivity and Feedback moved to Microphone Sensitivity and Feedback: Made this a regular article. It can still be included, but it also might be referred to as an ordinary, standalone article.

← Older revision	Revision as of 17:03, 16 April 2009
(No difference)

ST: mic replaced with microphone.

2009-04-16T16:55:45Z

mic replaced with microphone.

← Older revision		Revision as of 16:55, 16 April 2009
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	If you restore the level from the speaker by adding more gain at any trim or volume control, the difference between the level of the speaker at the microphone and from the voice is restored.		If you restore the level from the speaker by adding more gain at any trim or volume control, the difference between the level of the speaker at the microphone and from the voice is restored.

	When the added gain exactly compensates for the reduced ~~mic~~ sensitivity we have the same difference as before. If the microphone fed back at a certain level in the room before, it will do so again at the same level in the room. This is obscured by the other variables that tend to change when we pick a ~~mic~~ with a different sensitivity: different ~~mic~~ frequency response and polar pattern details, different placement, etc.		When the added gain exactly compensates for the reduced microphone sensitivity we have the same difference as before. If the microphone fed back at a certain level in the room before, it will do so again at the same level in the room. This is obscured by the other variables that tend to change when we pick a microphone with a different sensitivity: different microphone frequency response and polar pattern details, different placement, etc.

	The only way to get more gain before feedback is to lower the strength of the feedback path (the path between the speaker and ~~mic~~) while the feed-forward path (the path from the voice to the ~~mic~~) has the same gain. The ~~mic~~ has to be in a quieter part of the sound system’s coverage or the ~~mic~~ has to be directionally resistant to the speaker’s sound field compared to how well it picks up the desired input.		The only way to get more gain before feedback is to lower the strength of the feedback path (the path between the speaker and microphone ) while the feed-forward path (the path from the voice to the microphone ) has the same gain. The microphone has to be in a quieter part of the sound system’s coverage or the microphone has to be directionally resistant to the speaker’s sound field compared to how well it picks up the desired input.

	So it all comes down to one thing: when there is enough loudness in the room, how much better can the ~~mic~~ hear the desired source than it hears the sound system? Sensitivity doesn't enter into this equation.		So it all comes down to one thing: when there is enough loudness in the room, how much better can the microphone hear the desired source than it hears the sound system? Sensitivity doesn't enter into this equation.

Kjacob: Improving explanation for non-engineers

2009-04-16T15:50:29Z

Improving explanation for non-engineers

← Older revision		Revision as of 15:50, 16 April 2009
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	In the argument that follows, the assumption is that other variables in comparing two microphones are equal. In other words, only the sensitivity differs.		In the argument that follows, the assumption is that other variables in comparing two microphones are equal. In other words, only the sensitivity differs.

	Feedback occurs when the ~~loop gain of the whole system exceeds one. If you just decrease~~ the microphone ~~sensitivity, the sound in the room~~ is ~~less loud and the loop gain goes down by the amount of the sensitivity reduction. If you restore the level in the room by adding~~ more ~~gain~~ at any trim or volume control, we increase the loop gain again. When the added gain exactly compensates for the reduced mic sensitivity we have 1) the same level in the room as before and 2) the same loop gain as before. If the microphone ~~fed back at a certain level in~~ the ~~room before, it will do so again at~~ the same level in the room. This is obscured by the other variables that tend to change when we pick a mic with a different sensitivity: different mic frequency response and polar pattern details, different placement, etc.		Feedback occurs when the sound from the loudspeaker (or loudspeakers if a microphone is connected to more than one) is louder at the microphone than the sound of the voice.

	The only way to get more gain before feedback is to lower the strength of the feedback path (between speaker and mic) while the feed-forward path has the same gain. The mic has to be in a quieter part of the sound system’s coverage or the mic has to be directionally resistant to the speaker’s sound field compared to how well it picks up the desired input.		If you just decrease the microphone sensitivity, the sound from the loudspeaker goes down by the amount of the sensitivity reduction.

			If you restore the level from the speaker by adding more gain at any trim or volume control, the difference between the level of the speaker at the microphone and from the voice is restored.

			When the added gain exactly compensates for the reduced mic sensitivity we have the same difference as before. If the microphone fed back at a certain level in the room before, it will do so again at the same level in the room. This is obscured by the other variables that tend to change when we pick a mic with a different sensitivity: different mic frequency response and polar pattern details, different placement, etc.

			The only way to get more gain before feedback is to lower the strength of the feedback path (the path between the speaker and mic) while the feed-forward path (the path from the voice to the mic) has the same gain. The mic has to be in a quieter part of the sound system’s coverage or the mic has to be directionally resistant to the speaker’s sound field compared to how well it picks up the desired input.

	So it all comes down to one thing: when there is enough loudness in the room, how much better can the mic hear the desired source than it hears the sound system? Sensitivity doesn't enter into this equation.		So it all comes down to one thing: when there is enough loudness in the room, how much better can the mic hear the desired source than it hears the sound system? Sensitivity doesn't enter into this equation.

Kjacob: first edition

2009-04-15T19:25:28Z

first edition

New page

{{Bose Reviewed}}
It is a common misconception that a microphone that has lower sensitivity (in other words, a sound of a given intensity at the microphone produces a lower electrical signal than a microphone of higher sensitivity) is somehow more susceptible to microphone feedback.

In the argument that follows, the assumption is that other variables in comparing two microphones are equal. In other words, only the sensitivity differs.

Feedback occurs when the loop gain of the whole system exceeds one. If you just decrease the microphone sensitivity, the sound in the room is less loud and the loop gain goes down by the amount of the sensitivity reduction. If you restore the level in the room by adding more gain at any trim or volume control, we increase the loop gain again. When the added gain exactly compensates for the reduced mic sensitivity we have 1) the same level in the room as before and 2) the same loop gain as before. If the microphone fed back at a certain level in the room before, it will do so again at the same level in the room. This is obscured by the other variables that tend to change when we pick a mic with a different sensitivity: different mic frequency response and polar pattern details, different placement, etc.

The only way to get more gain before feedback is to lower the strength of the feedback path (between speaker and mic) while the feed-forward path has the same gain. The mic has to be in a quieter part of the sound system’s coverage or the mic has to be directionally resistant to the speaker’s sound field compared to how well it picks up the desired input.

So it all comes down to one thing: when there is enough loudness in the room, how much better can the mic hear the desired source than it hears the sound system? Sensitivity doesn't enter into this equation.