Detective Sonics

Damage to the ears from hazardous noise levels is gradual and subtle, and cannot be reversed. It is absolutely necessary, as an employer, for you to protect the hearing of your workforce with an exhaustive auditory protection program in cooperation with OSHA. Today we’re continuing our 3M PELTOR series with a look at the Sound Detector SD-200, which can be used to measure noise levels in a space to determine if hearing protection is required to work there. The SD-200 instantly provides this vital data at the touch of a button and with intuitive user-friendly interface. When sound levels surpass one of three user-set thresholds, indicators on the unit will flash from green to yellow to red, reflecting the rising auditory danger.


Another key feature for accurately assessing noise safety in your workplace is measurement integration. Most areas don’t have a single, unwavering noise level over the course of a day. Machines start and stop, go into periods of high and low activity, and so on. The consequences of equipping workers with protection that neglects those higher noise levels is obvious. You also don’t want to give your employees more protection than they need. With this reality in mind, the SD-200 automatically calculates the average sound pressure level (SPL) over the course of a testing session, allowing you to visualize the “shape” of the soundscape you’re dealing with. There’s a “play/stop” button that initiates the run-time sequencing, and different mode screens you can scroll through will tell you the SPL average, maximum, minimum, alert trigger, and calibrated figures. Noting these will give you a better idea of workplace risk, and OSHA likes to see precise data.


Going deeper, we have something called “frequency weighting.” The SD-200 has filter settings that approximate human hearing at different SPLs. A typical reading will be weighted towards “A” frequency. This causes the meter to mimic typical human response to noise at lower levels, excluding frequencies at the extreme ends of what we can hear. “C” frequency weighting, on the other hand, represents how the ear responds to extremely high noise levels. You probably won’t need a reading at that level though; unless extraordinary conditions are present, you should be find measuring the sound with A frequency weighting, slow time response, and an exchange rate of 3 decibels, which are factory default settings for each unit.


As far as care and maintenance goes, this is by no means an indestructible device. As the manual says, “this product is not intrinsically safe” in explosive or flammable environments. The lithium polymer battery can cause serious personal injury if it explodes, so make sure you’re using it in a stable environment and don’t try to open up the unit to get at the battery. The unit should never be submerged in liquid (it’s wise to keep it away from condensation as well, which can affect accuracy) or stored in temperatures above 70°C (158°F). The battery plugs into any USB port, but should be charged within a window of 0-40°C (32-104°F), well within the temperature range of an average room. It’s also worth using it as often as possible, as the battery has a limited shelf life whether or not it actually gets used.


All in all, the SD-200 is an impressive piece of technology that can take hearing protection beyond guesswork, allowing for a level of precision that ensures the best auditory health for your workers.

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