sound recording of turbo engine.

Recording is not really the issue, any good quality tape recorder, especially a mp3 style digital recorder would work fine.

The problem is how do you analyze the data?

I would suggest that rather than record sounds, purchasing a good accelerometer, and processing that signal in an FFT is what you are really after. Bruel and Kjaer makes a variety of sound recording an FFT processing systems. There are also a variety of other data acquisition systems that would work.

I like accels from PCB Piezotronics, and Data Physics makes a nice PC based four channel data acquisition system.

http://www.dataphysics.com/

An excellent answer and I ranked it as such. Use of FFT analysis should fill the bill on this one. This technique is how we analyze rolling mill cperating consistency to isolate mill failure modes.

yes, fft is very popular in vibration analysis and digital filter. today. many special tool for it. either hardware or software.

What you need is a mechanical analyzer. Probably an engine analyzer will be the easiest kit to find.

Problem is you need someone with experience to interpret the data as it isn't as easy as it might seem.

I used to sell oscilloscopes for Tektronix and we had engine analyzer sets. But we also had a guy who knew what he was doing that we brought along when a customer wanted to analyze mechanical systems.

Thanks Steve/mrehmus

Can you provide some more details of mechanical analyzer.

The answers above are correct. The problem is analysis. You would need to acquire data from as many engines as practical of the same model with all variations documented. Then when the engine failed or was repaired and issues found the problem would have to be correlated to the data.

Things like: starting vibrations; load vibrations; new vs normal; worn but still functional, etc. compared known failures etc. Then algorithms devised to speed the process to real time.

Excellent concept

Brad

http://cgi.ebay.com/Tektronix-Engine-Analyzer-System-Manual_W0QQitemZ7623444889QQcmdZViewItem#ebayphotohosting

Is an old Tektronix Engine Analyzer manual. Tektronix used to have a really good book on engine analysis. Unfortunately, I threw my collection away.

Most stationary engine (large engines) maintenance folks have analyzers so I assume you can find them and that equipment. Think Oil pipeline pumping engines. Major users of periodic engine analysis.

ratnagri posses an interesting question...

If you want to record extremely low frequency sound, say, 20 Hz >> .001 Hz, what do you use as an input device? I'm thinking that a common condenser mic is incapable of responding to these low frequencies. Furthermore, what about high frequency sounds, say, >> 20 kHz. I'm sure a condenser mic isn't going to handle these any better. So what do you use?

Some biologist made recordings of ultra-low frequency sound waves made by elephants. I'm sure she wasn't using a standard mic - if not, then what?!

Vermin,

That is partly why I suggested an accel. Most modern accels are 3dB at 1 or 2 Hz, and have high frequency capability from 5 to 20Khz depending on the model.

Very good question, Vermin. I would like to know too.

Anyway, no transducer is perfect but any transducer has a mechanical resonator that has to be "centered" in the range of expected frequencies. The lower the frequency, the larger the physical resonator (elephant size?) Maybe a sub-woofer in reverse? Tzunamies are in the same range.

if you would learned vibration and sound, yhou will know it.

There is a Danish company Brüel &Kjaer manufacturing sound and vibration analyzers. Check their homepage: http://www.bksv.com/11.asp

B&K company, a good ,old ,vibration test company from Danmark.

Get some good transducers and use a PC program like Spectra Plus. It is inexpensive (compared to dedicated analysers) and gives time, frequency, amplitude, and spectral graphics. Also has a 3-D time graphic which would let you see effects of rpm change.

Contact me if you need other details on the program. I have no connection to the company, and there may be others out there, better even. Check audio magazines for ads.

Great application! Could save money and lives.

Hi Bill.

So what is the frequency spectrum? If I had my perfect setup, it would cover 20KHz up to about 500KHz. And on the low end would handle 20Hz to as low as I could go. Do you know anything like that out there?

Thanks,

vermin-

greater than 20khz is ultrasonic.

you can use ultrasonic transducer. we have UT porject and UT instrument.

the probe is made of some crystal material. we have different probe for it as well.

frequency spectrum is a series of graphic of amplitude vs frequency.

for exmaple, the frequency spectrum of delta impulse is very wide from negtive infinite (math meaning) to + infinite. wheres a sine wave has one frequency. etc.