Looking for Practical Tips on conducting measurements according to ISO 3744 , ISO 3746

[BlueF16]

Hi all,

I'm suppose to conduct measurements according to ISO 3744 and ISO3746 on large generators, compressors and heat exchangers etc.

After reading the standards, the measurements seem to be quite cumbersome in their requirements.

I was hoping for general practical tips, on how you approach these measurements, what equipment you find makes it much easier for you to conduct these sort of measurements and anything you can add is appreciated.


Thanks,

Blue





This is my first post on this forum, I apologies in advance if this post doesn't comply with any rules or formats.

 

[Strong]

Even with a good background in acoustics and sound pressure level measurements, measurement of sound power on large machinery, either on a special test stand or in-situ, can be like a "trip to Fantasy Island". There are several vendors offering sound intensity/power measurement microphone system and software. I looked at the offerings about 2-years ago for a project that was terminated. A very interesting system is:

https://www.softdb.com/products/mezzo-sound-intensity-probe/

I have not used it nor sell it. I made my own sound intensity probe (2 condenser microphones) and can confirm it is far more difficult than making a property-line sound pressure level measurement!

Basic suggestions
Define purpose of the data; such as OEM PWL Rating, product development, or for noise control
Define instrument and testing requirements
Define actual or typical/expected sound environment (indoors or outdoors)
Identify access issues and means for locating microphone/probe
Identify actual or expected background sound sources and means of combating/correcting interference

If your sound experience is limited, then get an expert to at least do the first project!

Walt

 

[BlueF16]

Thanks Walt,

It very much does seem like a "trip to fantasy island".


Define purpose of the data; such as OEM PWL Rating, product development, or for noise control

The purpose of the data is noise control.​

Define instrument and testing requirements

I already have SVAN 959 to do this measurement.​

Define actual or typical/expected sound environment (indoors or outdoors)

Outdoor​

Identify access issues and means for locating microphone/probe

This is really where, i'm looking for advice. How do you successfully and efficiently translate the suggested microphone positions into 3D space with confidence ( Even if your answer is good old measuring tape) ​

Identify actual or expected background sound sources and means of combating/correcting interference

Have some thoughts on how to do so , and will take proper background noise readings.​

If your sound experience is limited, then get an expert to at least do the first project!

Yes, my sound experience is limited and I'm definitely in deeper waters than I should be. Thus, I'm trying to get educated before doing this. Getting an expert to do this is not an option currently, would have loved that though..​

Anything else you have to add would be great for me thanks.

 

[GregLocock]

I couldn't get access to the ISO, is this the 18 microphone in a hemispherical array on a hard surface? We did it once just to see if it told us anything the standard 5 microphone technique for engines gave. We did look at using Acoustic Intensity instead (hot wire, two mic, and surface velocity SEA), and that was occasionally useful, but basically the 5 microphone technique was our bread and butter.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Strong]

SVAN 959 is a sound pressure level meter (single microphone)and not a sound intensity probe. Sound Power measurement methods (if that is your requirement) is rather limited for your instrument; especially for large machines in outdoor plant environment. At the minimum you need a microphone extension cable to mount microphone at end of a pole. I prefer to break the measurement surface into small areas and do time averaging while "painting" the small area by moving the microphone. The time-averaged overall level and spectrum would then represent a portion of the total surface area.

Walt

 

[Strong]

I have used omni-directional microphones (like your sound meter), directional and pressure gradient microphones, shielded omni-microphone (close to surface), and sound intensity probe (2-pressure microphones) on various projects. I have also used a high temperature microphone for in-stack measurement for ID fans. The measurements were intended for noise control (source identification and contribution) and not for sound power rating. I have used handheld meter and microphone/probe, short and long extension poles for remote microphone, and in combination with ladders and man lift to gain access. Obviously one can get creative (time and cost) to setup apparatus for holding, moving, and measuring 2D and 3D position. It would generally be more doable for outdoor measurements of machines at a test facility as compared to machine at an operating plant. Here is a search link that may be of interest:
Search: practical sound power measurements

https://www.bing.com/search?q=pract...gDsIO3GCeb94C0i6pBihZ9YFCsvQN2CD8I7Ie&plvar=0

Old but good reference for using a sound meter:

https://docs.lib.purdue.edu/cgi/vie...ext=icec&=&sei-redir=1&referer=https%3A%2F%2F

http://www.bing.com%2Fsearch%3Fq%3D...0#search="practical sound power measurements"

I would have to know a lot more about your project before offering any other "tips".

Walt
w_f_strong@msn.com