Both class 1 and class 2 SLMs can be used to take things like workplace noise, community noise, industrial noise, and other commercial or residential noise measurements. Keep in mind that class 1 SLMs are the most expensive. Though class 3 SLMs are not considered accurate enough for most noise measurement purposes, it is acceptable to use one to take a rough preliminary measurement that lets you know if you need to take a more precise measurement with a class 1 or class 2 SLM. The easiest place to find a sound level meter to purchase is online. Class 2 meters start at around $150 USD and class 1 meters start around $350 USD.
If you don’t have a physical owner’s manual, you can find manuals for most common sound level meter models online. Look up a manual for your SLM model by brand and name on a search engine to find exact calibration instructions. For example, some SLMs come with an acoustic calibrator that you mount over the microphone to calibrate the meter. It emits a constant sound level, typically 93dB, for the microphone to read in order to calibrate itself.
For most SLMs, it doesn’t matter how you point the mic, but you can point it directly at the noise source or consult the manufacturer’s instructions for specific directions to be sure.
Some more advanced models allow you to take measurements at a slower speed or at different intervals to measure intermittent sound levels.
For instance, a 100dB sound pressure level at 100 hertz (Hz) would be heard by the human ear at the same loudness as 80dB at a 1000Hz frequency. A-weighted decibel readings give you a more accurate interpretation of how your hearing may be affected by noise at different frequencies by telling you at what volume your ears hear the sound, rather than just the overall loudness. Keep in mind that noise levels higher than 85dB can start to damage the human ear after 8 hours of listening. Noise levels of 100dB can damage your hearing after just 15 minutes.
Some examples of top-rated sound level meter apps available for both Android and iOS are SPL Meter (free), Decibel X (paid), and Too Noisy Pro (paid).
For example, you could use an app to measure the sound levels at a concert, sporting event, workplace, or other noisy space. This can help you determine if the sound levels are potentially harmful. Most apps will immediately start showing you a fluctuating sound level measurement when you launch them.
For example, in the NIOSH app, the button is a triangular play-type button in the lower left-hand corner. Some apps might only show you fluctuating instantaneous sound levels and not record sound measurements.
If you recorded for too short or too long of a time period, there is usually a reset or clear button to start over.
For example, in the NIOSH app, the metrics include the total run time, instantaneous dB, LAeq, max sound level, and a time weighted average for the noise level. Some apps let you save different measurement recordings and view them over time graphs. Play around with whichever app you downloaded to get to know all the different features and settings. The difference between regular decibels and A-rated decibels is that dbAs are adjusted according to the way the human ear hears sound. For instance, 100dB at 100Hz is equivalent to 80dB at 1000Hz. A dbA reading tells you at what level your ears are perceiving the sound, instead of its actual volume in decibels.
