Share thisSound plays a vital role in society as the mechanism by which hearing is made possible through pressure waves. Unfortunately, if the sound pressure levels get too high, there is a negative impact on animals and structures.
The levels of sound and vibration an entity can withstand are a function of size and makeup. In the lab animal facility setting, noise, sound, and vibration affect the life cycle, interaction, and behavior of animals. However, the impact of noise, sound, and vibration is a largely undocumented factor in the research. Environmental impacts, such as noise, may have an impact on interactions like social behavior, and need to be considered in more detail during the design phase of animal research facilities.
Definition of Sound, Noise, and Vibration
Commonly, there is misunderstanding and confusion about noise and sound as it applies to individual interactions and facility design. Hence, for clarity it is important to understand the difference between sound and noise. Sound is a mechanically radiated energy that is transmitted by longitudinal pressure waves in a medium, such as air.1 Comparatively, noise is any sound that is undesirable or interferes with one’s hearing. Thus, it is possible to have sound that is classified as noise. In comparison, vibration is a periodic motion of particles in an elastic body (rigid or semi-rigid structure) moving in alternatively opposite directions from the position of equilibrium. Vibration is a driving force behind radiated sound and should be highly considered during the design process.
Sound and Vibration Exposure
To date, sound exposure limits have not been standardized for laboratory animal settings as they apply to the test subjects. However, for humans, the Occupational Safety and Health Administration (OSHA) oversees the exposure limits as they relate to sound. The limits set forth by OSHA are thresholds to prevent permanent hearing loss. The current exposure limit for an eight hour day without hearing protection is a continuous 85 dB.2 Exposure to levels in excess of 85 dB for an eight hour day is permitted with the use of hearing protection. Should hearing protection be unavailable, the time of exposure needs to be reduced. Specifically, for every 3 dB above 85 dB, the allowable time of exposure will reduce by half. As an example, a 94 dB continuous sound level will permit a one hour exposure. Figure 1 shows the breakdown of exposure limits.
In addition to hearing, sound and vibration can have a physical impact on animals. The amplitude and frequency of disturbances coupled with body structure should be considered when determining acceptable exposure limits. Smaller animals are more susceptible to the affects of sound and vibration over time and will adapt or adjust accordingly. In some cases, mutations may result from exposure to undesirable conditions. Therefore, conditions unnoticed and acceptable for human occupancy may have a dramatic impact on animal colonies due to their increased sensitivity and size.