acoustic sensor efficiency

[Higgler]

Can anyone suggest an acoustic sensor reference.

We are about to implement an array of acoustic air sensors in a housing and I'd like information regarding improving/optimizing sensor efficiencies.

I'm wondering if sensors should be isolated in the air, or maybe potted in the housing, i.e. mounted rigidly.

It's a new area for me, hence my question. I have done some googling, but can't find sensor efficiency vs. mounting configuration answers.

thanks,
kch

 

[GregLocock]

Do you mean actual efficiency - electrical power out / acoustic power in?

Or do you mean sensitivity, and frequency response, and signal to noise ratio etc?

Assuming the latter -it depends to a large extent on what vibration the housing sees, but most acoustic sensors (can we just call them microphones?)are mounted rigidly into a casing which is then somewhat flexibly mounted into a larger structure.

This is all a bit hand wavy, you need to be far more specific about what you are looking for.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

I just saw a movie where the singer's microphone was suspended with springs from an exterior ring, ca. 1925, presumably to prevent vibrations from propagating to the microphone from the stand.

The main issue here is whether the housing transmits vibrations into the microphones, and whether you consider that to be desireable or not. That will dictate your course of action on whether to float the microphones or not. I would think that you'd need to run some tests no the housing, in any case.

TTFN

FAQ731-376

 

[Higgler]

I have a small housing, say cigarette pack size with 5 acoustic sensors (they tx, then rx the acoustic bounce off nearby walls - 2-20 feet away). Acoustic sensors will be bonded into this small housing. I need to mount this housing on a tube, and I was wondering a couple of things.

1) should the small housing be epoxied filled to give the acoustic sensor some more mass to push against, or should I leave the housing air?
2) regarding attaching this cigarette pack size housing to a tube, should I do it loosely with velcro or tightly with adhesive.

The tube is mounted to a rotator to take acoustic patterns. I read there are reference acoustic sensors to get a measurement similar to antenna gain references, but we don't plan to use them, at least initially.

I was thinking that either loose or rigid mounting of a sensor might create resonances and degrade the acoustic sensor performance. Since I'm a rookie (again), I'd really like to find some direct info from experienced acoustic sensor afficionado's plus get some reference material to show the boss "see...it says to do it this way in here, that's why I used bubble gum to attach it"

thanks,
kch

 

[IRstuff]

When you say acoustic, do you mean ultrasonic?

For ultrasonic, it matters not. I've seen sensor/emitter mounted on PC boards with nothing else. The emitter doesn't need to "push" against anything. The amount of energy being transmitted is usually so small that the mass of the emitter package is enough to kill the motion.

TTFN

FAQ731-376

 

[Higgler]

It's a 45 khz frequency transmitter. Maybe that makes it ultrasonic.

kch

 

[GregLocock]

Start by mounting it the simplest and most convenient way, velcro sounds fine. If it tends to pick up noise from the mechanism then you may need a better isolation system, but that sounds reasonable to me.

45 kHz is ultrasnic, as IRstuff says, they are pretty tolerant, leastways I have them hanging off a pcb on a robot and they work fine.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IRstuff]

I guess you're not used to such low frequencies; I seem to recall most of your previous postings having to do with RF or microwave. ;-)


TTFN

FAQ731-376

 

[Higgler]

Yup, it's a new area. I'm mostly antennas, but have some work on these sensors.

What I'd really prefer to work on is my golf game.

kch