How do you know if you need to conduct a general sound survey? There are several indications:

• you have to speak loudly at arms length to communicate,

• employees complain that the noise bothers their ears,

• workers indicate that when they leave work, their ears "ring," speech sounds muffled, or the TV needs to be turned up, or

• the readings using an inexpensive sound level meter (e.g., from Radio Shack) show areas above 80 dB when set to the "A" scale.

If the measurements in either the broad area or detailed surveys were made in the hearing zone of employees, the data can be used to determine employee noise exposures. However, information on how much time employees spend in the different areas monitored is needed.

The equipment used to conduct a general noise survey must meet OSHA and ANSI specifications if the measurements are to be used for determining employee noise exposures. The sound level meter must have a ANSI Type I or II precision rating. In addition, a calibrator must be used to verify the accuracy of the meter.

When noise is steady, reading a conventional sound level meter is simple. This is because the needle movement is also steady. However, when the noise is fluctuating or intermittent (which is more typical than not), excessive needle movement makes it difficult to obtain an "eyeball" average.

To ensure the repeatability of measurements, we use "integrating" sound level meters. This type of meter contains special circuitry that computes the average noise level (called the equivalent level or Leq) and eliminates the inconsistency of obtaining readings from a "bounding" needle. When two separate Leqs are in agreement, the measurement is considered repeatable and reliable.