Help on NI Speedy-33 (2 questions)

[BK Lian]

Hi,

Q1) Do anyone know what is the sensitivity level (mV/Pa) of the two onboard microphones on the Speedy-33?

Q2) Upon accquiring the data from the analog input AI0 and AI1 (Elementary I/O node), what is the measurement in? Voltage?

Note: From the datasheet specification, the maxi working voltage for the analog input is 600mV.

Thanks in-advance.

[Mathan]

same topic here

[BK Lian]

Yes, it is posted by me too. However, I did not get the specific answer I'm looking for... 😞

[Mathan]

Hai,

Please wait patiently for sometime. Somebody will surely help you in solving your problem. If you are posting in separate threads several times, it will lead to confusion and people will start avoiding those threads. Please wait patiently for sometime.

Thanks for your understanding,

Mathan

[Edit: Please see your other thread, somebody asked to give ur mail id to help you. Hope your problem will solve soon. All the best.]

Message Edited by mathan on 03-17-2009 03:28 AM

[JK1]

Hai,

I looked into manuals of speedy board but there was nothing relevant to sensitivity of microphones.

NI should have the answer for your questions.

Is there a comment from NI??

[BK Lian]

Hi,

Mathan: Sorry if I've caused confusion. It is because the way I phrase my earlier post is much more "complicated". So I've decided to post another question which is more specific for others to answer.

JK: Ya, I've emailed the NI support engineer on Speedy-33 issues. No reply yet (finger-cross).

Thanks guys!

[Coq_Rouge]

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BK Lian wrote:

Hi,

Q1) Do anyone know what is the sensitivity level (mV/Pa) of the two onboard microphones on the Speedy-33?

---

It is hard to know this without knowing the manufacturer. I guess even NI will have some problems finding this data. This microphone is not meant for advanced audio measurement. The OEM manufacturer has probably selected the cheapest microphone, with just descent enough performance.

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BK Lian wrote:

Q2) Upon accquiring the data from the analog input AI0 and AI1 (Elementary I/O node), what is the measurement in? Voltage?

Note: From the datasheet specification, the maxi working voltage for the analog input is 600mV.

---

 The microphone picks up mechanical energy and converts it to electrical energy. Between the microphone and the AD converter you will most certain find a gain stage. The AD converter converts the voltage passed to it. The output from the AD represent a footprint of the mechanical energy converted to electrical energy. If the  microphone has a more or less linear transfer curve regarding sound pressure in the audio range (20-20Khz). The output level from the AD converter will have a linear numerical relationship with sound pressure. But to find this relationship you need some sort of precise and accurate calibration with professional equipment. If not professional your project will not be very accurate. Your accuracy depends very much on your calibration equipment. But this is a school project, so the main goal is learning, not to present a production ready prototype. So do your best with professional the resources you have available. But remember to discuss the accuracy in your final report.

Good luck 

[JK1]

Hai,

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he output level from the AD converter will have a linear numerical relationship with sound pressure.

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Yes the  output will be linear.  But there are weighting namely A-weighting,B and C which converts this linear response to lograthemic response which is equivalent to human ear.  Using this weighting the weighted output can be obtained based on which the calculations should be done.

The accuracy gets sacrificed due to lack of caliberation as mentioned in the above post this setup helps in learning.

[Coq_Rouge]

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JK1 wrote:

Hai,

Yes the  output will be linear.  But there are weighting namely A-weighting,B and C which converts this linear response to lograthemic response which is equivalent to human ear.  Using this weighting the weighted output can be obtained based on which the calculations should be done.

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This is absolutely correct, I did not mentioned it because I was sure BK Lian was aware of this problem. If not I recommend Google and the phrase "human hearing curve"

[BK Lian]

Hi Guys,

To summarize,

1) the ambient "sound" pressure level (mechanical energy) is converted to electrical energy via the onboard microphones.

2) It is converted from analog to digital signal via A/D converter with 16 bits resolution.

3) A gain (depending on the gain setting) is applied to the signal and reflected on the waveform graph.

4) Weighting filter (usually A-weighted) is applied which response to the human sentivity hearing range (1-4kHz) for better illustration/understanding of what is being measured.

Hence, it is possible to implement the A-weighted filter using the LabVIEW Digital Filter Design toolkit (I know S&V measurement has it but it cant be executed in DSP module)?

Thanks!

Regards,

Bee Kwang