Gracey & Associates Hire and Calibration

Sound Level Meters and Noise Exposure Measurements

We specialize in the hire of noise meters, supplied by the leading manufacturers and have the most comprehensive range in the UK.

All our meters, microphones, accelerometers etc., are delivered with current calibration certificates, traceable to UKAS. Our ISO 9001 laboratory is audited by British Standards and we are Sponsor Members of the Institute of Acoustics.

We are an independent organization with over 30 years experience of sound and vibration solutions.

Hire is the cost effective solution with overnight access to the latest and best instrumentation.

Gracey & Associates   01933 624212

Sound and vibration instrument hire and calibration

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B&K 2236    Sound Meter - type 1 B&K 2238    Noise Meter with Filters - type 1 B&K 2250    Noise Monitoring Equipment - type 1 B&K 2260    Sound Insulation and Sound Intensity Meter - Class 1 CEL 350      Personal Sound Exposure Meter - dBadge CEL 460      Noise Dosimeter - type 2 CEL 593      Real Time Sound Level Meter - type 1 Nor 116       Sound Level Meter - type 1 Nor 118       Sound Meters, Real Time - type 1 Nor 118 +    Sound Level Meter, Real Time - type 1 Nor 140       Sound Level Meter, Real Time - type 1

Gracey & Associates   01933 624212

BSI accreditation for instrument hire and calibration

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Sound Level Meter Basics
Sound meters have been around for many years. In the beginning sound level meters were very expensive, heavy and didn't do very much. They were effectively a microphone and a voltmeter with a 1 second [SLOW] time constant to slow down the meter fluctuations, so you could average them by eye.

Modern sound meters are much smaller and process the data in more and more complex ways, but the accuracy of the measurements still rely on the quality of the microphone. Manufacturers of measurement microphones go to great lengths to ensure the microphone responds uniformly to sound waves approaching from above, from the side or straight ahead.

This is not too difficult at say 256 Hz or middle C on a piano where the wavelength of the sound is very long compared with the size of the microphone. Even at 4 times this frequency, reasonable quality microphones can accurately follow the signal if it is coming from directly ahead or only a few degrees off centre. But at 10 times the frequency only the best microphones are still responding equally and if we want to measure to the upper limits of hearing, say 20,000 Hz or nearly 100 times higher than middle C, then a remarkable microphone [Type 1 sound level meter] is required. Well before you get to these frequencies the wavelength of the sound wave are comparable with the dimension of the microphones and all sorts of horrible and complex sound fields defeat only the very best microphones from faithfully supplying the 'voltmeter' with an accurate voltage proportional to the original sound wave.

Some factories produce millions of microphones at 1 penny each or less for use in cheap audio products, so buyer beware. Measurement microphones are very expensive to produce as they are very labour intensive and the manufacturing process, including the required 'ageing' can take months.

The microphone can be compared to the Hi-Fi loudspeaker, one converts sound waves into electrical signals and the other converts electrical signals back into sound waves. A good quality speaker system includes woofers, mid-range speakers, tweeters and cross-over networks in an attempt to cover the range of hearing up to 20,000 cycles per second [20 kHz]. Few manage it without 'colouration' and they cost hundreds of pounds. We expect and British Standards demand that sound level meter microphones to do the same thing, so we should not be surprised if measurement microphones also cost hundreds of pounds.

It follows therefore that you can use the latest computer based sound level meter but the results will only be as good as the microphone that transformed the original sound wave.

Many of our customers have noise measurements thrust upon them and for a short period in their lives they are expected to understand the terms and sometimes complex parameters we use every day. If you would like basic information on other sound and vibration topics click here.

Gracey & Associates   01933 624212

BSI accreditation for instrument hire and calibration

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speed links - accelerometers l bruel & kjaer l building acoustics l construction and demolition l environmental noise l hand-arm vibration - havs l health and safety at work l larson davis l microphones l noise and vibration at work l noise meters l noise pollution l noise sources l norsonic l seismographs l sound insulation l sound intensity l sound level meters l sound power l standards l vibration l vibration white finger l vibrock l whole body vibration

over 500 pages of information plus a glossary with hundreds of terms and parameters and our calibration service.