Noise in a laboratory animal facility from the human and mouse perspectives

Abstract

The current study was performed to understand the level of sound produced by ventilated racks, animal transfer stations, and construction equipment that mice in ventilated cages hear relative to what humans would hear in the same environment. Although the ventilated rack and animal transfer station both produced sound pressure levels above the ambient level within the human hearing range, the sound pressure levels within the mouse hearing range did not increase above ambient noise from either noise source. When various types of construction equipment were used 3 ft from the ventilated rack, the sound pressure level within the mouse hearing range was increased but to a lesser degree for each implement than were the sound pressure levels within the human hearing range. At more distant locations within the animal facility, sound pressure levels from the large jackhammer within the mouse hearing range decreased much more rapidly than did those in the human hearing range, indicating that less of the sound is perceived by mice than by humans. The relatively high proportion of low-frequency sound produced by the shot blaster, used without the metal shot that it normally uses to clean concrete, increased the sound pressure level above the ambient level for humans but did not increase sound pressure levels above ambient noise for mice at locations greater than 3 ft from inside of the cage, where sound was measured. This study demonstrates that sound clearly audible to humans in the animal facility may be perceived to a lesser degree or not at all by mice, because of the frequency content of the sound.

Figure 1.

Physical plant configuration of vivarium module where noise testing occurred.

Figure 2.

Sound pressure levels produced from ambient noise, the ventilated rack blower, and ventilated rack blower with the animal transfer station (ATS), as measured from inside of the cage. The human and mouse audiograms are superimposed on the graph. Measurement of the sound pressure levels that existed within each audiogram were made by determining the decibel level of sound pressure within the δ zone (area between the violet vertical lines). For example, the sound pressure level within the mouse audiogram is demarcated. Data are presented on (A) a linear scale to show the trend of data at all frequencies, as well as on (B) a log scale so that more detail can be seen at the lower frequencies.

Figure 3.

Sound from the ventilated rack blower only and with the animal transfer station (ATS) measured from inside of the cage and compared with ambient noise. Both the A-weighted (a, P ≤ 0.05) and linear (b, P = 0.05) levels of sound pressure for humans increased due to the ventilated rack blower as compared with ambient noise. The linear sound pressure level for mice was lower (c, P ≤ 0.001) relative to the human linear level of sound pressure for both ambient noise and the ventilated rack blower only. Although sound pressure increased in the human hearing range as a result of the ATS, the linear sound pressure level in the mouse hearing range was not increased above ambient noise or blower-only levels. Each bar represents the mean ± SEM with 2 degrees of freedom. Due to technical issues, data from the ventilated rack blower with ATS could be used from only 2 locations and therefore were not included in the statistical analysis.

Figure 4.

Intracage sound pressure levels from various types of construction equipment as measured 3 ft from the equipment. The human and mouse audiograms are superimposed.

Figure 5.

Sound pressure levels from the large jackhammer as measured at various locations.

Figure 6.

Sound pressure levels from the shot blaster as measured at various locations.