Workers, including lab personnel, tend to develop their own internal lingo in professional settings, where colleagues often work alongside each other for years. While lab shorthand can be useful—and sometimes even entertaining—it’s no substitute for clear communication using well-defined terms, especially where lab safety is concerned.
In a prior post, we took a look at the history and early usage of the decibel, a humble and ubiquitous term that’s used in many conversations about noise safety in the lab. This time around we want to consider some of the ways decibel measurements are used in scientific situations. We’ll also cover some of the most common decibel abbreviations, which could figure into lab safety discussions concerning noise.
The Pressure of Sound
Decibels are used to measure sound in a surprising number of capacities. As we discussed previously, humans often perceive noise in terms of intensity. Particularly loud noise has been described, for example, as “a wall of sound.” Sound intensity or “sound pressure level” (SPL) is measured in decibels (dB). A measurement of 0 dB corresponds to an SPL of 0.0002 microbars, which is the point at which humans without hearing loss are able to perceive a sound.
Since our ears’ hearing capacity, as well as decibel measurements, increase logarithmically (by a factor of 10), 120 dB—which is beyond the noise safety level of 85 dBA, as determined by the Occupational Safety and Health Administration—describes a change in sound pressure level of compared to the 0 dB threshold level.
But the dB isn’t just used for measuring sound. For example, amateur radio is another place where decibels matter. Electronic and radio circuits must be able to handle signal levels that vary by many orders of magnitude. High frequency (HF) band signal strength is measured in S units, which correspond to a change in strength of between 5 and 6 dB. However, most amateur radios are not calibrated to the high degree necessary in modern lab equipment, and the standard change in signal strength of one S unit is generally considered to be 4 dB.
Sound and amateur radio are just two examples of decibels in action, but there are actually more uses. You will note that in many circumstances, the “dB” is followed by an additional abbreviation (as in the OSHA noise safety limit mentioned above). Such abbreviations indicate a specific reference value. For example, power levels are given in dBm, where “m” stands for milliwatt. Here, 0 dBm corresponds to 1 milliwatt of power, while 10 dBm correlates to 10 milliwatts. These reference numbers are frequently used to make system calculations easier and to indicate which capacity the dB measurement is being used in.
Noise Safety and dBA
The decibel suffix that occurs most frequently in our work at IonBench involves an appended “A”—written dBA, dBa, or dB(a). This stands for “adjusted” and is the relative noise safety level as perceived by the human ear. “A” refers to a necessary adjustment to reduce the decibel values of sounds at low frequencies, in comparison to unweighted decibels at higher frequencies. This adjustment is made because the human ear is less sensitive to low audio frequencies, especially below 1,000 Hz.
Talking Lab Safety
We hope you have found this decibel primer helpful. We know that sometimes the human perception of an indefinable “wall of sound” can make it difficult to discuss aspects of noise safety. Perhaps this overview of decibels can help facilitate internal lab discussions going forward, making lab safety conversations easier to have and to understand.
If you have further questions about decibels or the dedicated lab furniture we’ve crafted to minimize sound hazards in your lab, contact Tim Hawkins today at firstname.lastname@example.org or 888-669-1233.