The classic GenRad instrument line including RLC standards and decades, Digibridges, LCR meters, megohmmeters, stroboscopes, and sound level meters continues to be manufactured and supported by IET Labs, Inc . in West Roxbury, MA.
42.
Until 2003 there were separate standards for exponential and linear integrating sound level meters, ( IEC 60651 and IEC 60804 both now withdrawn ), but since then the combined standard IEC 61672 has described both types of meter.
43.
This change was needed as each sound level meter manufacturer could choose their own low and high frequency cut-offs ( & ndash; 3 dB ) points, resulting in different readings, especially when peak sound level was being measured.
44.
As for calibrating sound level meters, ours actually came with a calibrator that, when closely coupled with the meter's microphone, puts out a 94 dB 1000 Hz tone ( or, with a switch press, a 114 dB tone ).
45.
The old B-and D-frequency-weightings have fallen into disuse, but many sound level meters provide for C frequency-weighting and its fitting is mandated & mdash; at least for testing purposes & mdash; to precision ( Class one ) sound level meters.
46.
So, if you have various trains going at different speeds affecting you in your house, perhaps the most sensible thing to do would be to buy a sound level meter ( usually called a decibel meter ) and measure the difference.
47.
:: Radio Shack, by the way, sells sound level meters for not very much money; the meter I use at home came from there ( whereas the work meter and calibrator that I was describing above is a very nice Br�el and Kjaer ).
48.
A-weighting is also in common use for assessing potential hearing damage caused by loud noise, though this seems to be based on the widespread availability of sound level meters incorporating A-Weighting rather than on any good experimental evidence to suggest that such use is valid.
49.
The alternative method which is to generate a time history by storing and displaying samples of exponential sound level has too many artifacts of the sound level meter to be as valuable and such sampled data cannot be readily combined to form an overall set of data.
50.
The international body that specifies the technical requirements of such instruments as sound level meters and dosimeters is the International Electrotechnical Commission ( IEC ) based in Geneva; whereas the method of their use is normally given in an International Organization for Standardization ( ISO ) publication.
