[[email protected]]

http://www.analog.com/library/analog...crophones.html

Mark

[Jay Ts]

Mark (makolber) wrote:
http://www.analog.com/library/analog...rchives/43-02/
mems_microphones.html

Thanks. I'd looked into this years ago, and was quickly
turned off by the frequency response curve and noise
of the accelerometers that were available at the time.

It's interesting to read the paper, to see the
idea explored a little. They've come out with some
better products than the ones I read about before,
and maybe someday they will be practical for "pro audio"
applications. I only vaguely remember what I had learned
about the basic technology -- getting a sufficiently low
noise floor from the devices may be difficult(?).

Jay Ts
--
To contact me, use this web page:
http://www.jayts.com/contact.php

[Ben Bradley]

On Thu, 5 Feb 2009 06:56:38 -0800 (PST), wrote:

http://www.analog.com/library/analog...crophones.html

I'm reading through this, the article talks about Jimi Hendrix and
feedback leading up to this, but still ... I'm trying really hard to
ignore this:

"Figure 7. Accelerometer mounted on Fender Stratocaster acoustic
guitar."

I know they've been making Strats for over a half century, but
somehow I missed the introduction of the acoustic model.



Mark

[Ben Bradley]

On Thu, 05 Feb 2009 23:45:35 -0500, Ben Bradley
wrote:

On Thu, 5 Feb 2009 06:56:38 -0800 (PST), wrote:

http://www.analog.com/library/analog...crophones.html

I'm reading through this, the article talks about Jimi Hendrix and
feedback leading up to this, but still ... I'm trying really hard to
ignore this:

"Figure 7. Accelerometer mounted on Fender Stratocaster acoustic
guitar."

I know they've been making Strats for over a half century, but
somehow I missed the introduction of the acoustic model.

I did find this Fender "Stratacoustic" model, but still, you'd
think they'd find some model of Martin to put this on. Or maybe they
didn't want to risk scratching up a Martin by attaching things to it.

http://www.fender.com/products//sear...tno=0967400306




Mark

[Arny Krueger]

wrote in message


http://www.analog.com/library/analog...crophones.html


What they don't talk about is dynamic range for acoustical inputs. Probably
not all that good.


Accelerometers have been used as feedback elements for loudspeakers for
several decades. Traditional accelerometers have been relatively massy,
which limits their use at frequencies above 100 Hz. Accelerometer sensing
based inverse feedback works.

Those traditional accelerometers have had good response to at least 1 KHz,
but their mass was the stumbling block. These look like they may be far
lighter. I suspect that accelerometers would find their way into more
speakers if they were less expensive and could provide stable results to say
600 to 2000 Hz.

[[email protected]]

On Feb 6, 7:38*am, "Arny Krueger" wrote:
wrote in message



http://www.analog.com/library/analog...3-02/mems_micr...

What they don't talk about is dynamic range for acoustical inputs. Probably
not all that good.

Accelerometers have been used as feedback elements for loudspeakers for
several decades. Traditional accelerometers have been relatively massy,
which limits their use at frequencies above 100 Hz. * Accelerometer sensing
based inverse feedback works.

Those traditional accelerometers have had good response to at least 1 KHz,
but their mass was the stumbling block. These look like they may be far
lighter. *I suspect that accelerometers would find their way into more
speakers if they were less expensive and could provide stable results to say
600 to 2000 Hz.

Arny,

that's a good point, the new MEMs devices might make speaker
linearization w/ feedback more practical then it was in the past.

Mark

[Scott Dorsey]

Arny Krueger wrote:
wrote in message


http://www.analog.com/library/analog...crophones.html

What they don't talk about is dynamic range for acoustical inputs. Probably
not all that good.

It's not, really, but it gets better every day. The dynamic range issues
on the MEMS microphones are pretty severe because of the small area of the
diaphragm, and the low mass of the accelerometer beams cause similar issues.

In most accelerometer applications, though, bandlimiting can help improve
dynamic range. And a lot of these are being used in go/no go applications
like firing off automotive airbags rather than in applications requiring
low noise and high linearity like inertial navigation systems.

Those traditional accelerometers have had good response to at least 1 KHz,
but their mass was the stumbling block. These look like they may be far
lighter. I suspect that accelerometers would find their way into more
speakers if they were less expensive and could provide stable results to say
600 to 2000 Hz.

Yes, the Velodyne feedback subwoofers have been using MEMS accelerometers
for a few years now. It's a good choice for the application.

You are starting to see MEMS microphones being used in cellphones as well,
because they can be designed with A/D conversion directly on the same chip
as the microphone, and because they perform better in high humidity and
when actually wet than do electrets.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."