We’ve talked before about the importance of controlling noise levels in the lab. Being able to communicate clearly and effectively is critical for lab safety, and being unable to hear another’s voice or distinguish what they are saying is a true safety hazard.
There is more to this issue than the distraction of noise, however. To understand how sound can be dangerous, it’s important to understand the two important characteristics behind noise: frequency and volume.
As we all learned in high school or college, sound is created by a varying pressure wave that travels through a medium—most commonly air. As that pressure wave travels, it changes atmospheric pressure in a periodic rhythm. The frequency of sound is defined by the number of pressure variations it causes. It is measured by the hertz, a unit of frequency equal to one cycle per second.
From a perception standpoint, our brain translates higher-frequency sounds as having a higher pitch. This is why, say, the piccolo sounds higher and chirpier to us than the bone-resonating bass drum when we hear a marching band play.
The second property of noise is its loudness. A louder noise has a larger pressure variation than a weaker one. The variations in pressure are measured in pascals. However, the human ear can hear things much softer than a single pascal, so measurements of softer sounds are often given in units of micropascals.
From a perception standpoint again, that marching band will sound louder as it’s coming toward you in part because the atmospheric pressure waves of frequency are being pushed toward you as the band gets closer. As it moves away, some of the brass instruments are pointing away from you, which decreases the volume as atmospheric pressure is pushed away.
Decibels and A-Weightings
Because the human ear can detect quite a wide range of sound loudness, the logarithmic decibel scale was developed to more easily express a wide range of volume. For example, a full symphony orchestra can have a loudness rating of 2,000,000 micropascals, while the softest sound we can detect is just 20.
By using a base 10 and defining that 20 micropascals as 0 decibels, we can more easily approximate the effect of relative loudness. Furthermore, the ear responds to logarithmic changes in levels naturally corresponding with the decibel scale.
On the frequency side, the human ear can hear sounds ranging from 20 to 20,000 hertz. To again make these numbers more comprehensible, the audible frequency range has been divided into 8 octaves (a musical term). These octaves are further divided into thirds, giving us 24 one-third-octave bands for categorizing the frequency of sounds.
Since the ear also does not correlate frequencies linearly, these bands have been given A-weightings, which reduce the impact of the highest- and lowest-pressure bands. This corresponds to the actual impact on the human ear, which is most sensitive to frequencies from 2,500 to 3,000 hertz.
Sound, Noise, and Lab Safety
When assessing the impact of specific noises in a lab, all these factors are usually measured in terms of dBA, or an A-weighted decibel reading.
Of course, a single sound seldom occurs all alone; We usually hear multiple sounds all at once, such as a conversation in the lab, running water in a sink, the fume hood in use, and the mass spectrometer vacuum pumps churning away. Together these can add up to quite a lot of pressure on the eardrums, not to mention the brain that is tasked with separating and classifying each type of sound.
Thanks to measurements like dBA, researchers are able to make more informed decisions when determining whether a piece of dedicated lab furniture will contribute to a safer lab environment. For example, our IonBench comes with a guaranteed MS vacuum pump noise suppression of 15 dBA, or 75%, which would significantly improve your ability to hear the other important sounds in your lab.
Clearly, reducing noise in the laboratory should be a priority to ensure a safe, efficient work environment. To learn more about how our dedicated lab furniture can contribute to safety in your own laboratory, contact us today.