10.3 Flushing Toilet Noise

10.3 Flushing Toilet Noise

The purpose of this study is to identify factors of the flushing noise of an upstairs toilet, which despite having a low SPL caused annoyance for an apartment resident. We analyzed the temporal and spatial factors of the flushing noise from an upstairs toilet to the head position on a bed, because the resident was very annoyed during sleep. The noise signals were picked up by half-inch condenser microphones placed at two ear entrances on the spherical dummy head, which had been used for the aircraft noise measurements mentioned in the previous section.

The plans of the upstairs and downstairs are shown in Fig. 10.7, wherein recording was performed on two nights (Kitamura et al., 2002). During the measurement, all windows and a bedroom door were closed, and the air conditioner was turned off. The measured temporal factors extracted from the ACF are shown in Fig. 10.8. Solid lines indicate values for a typical example of the flushing toilet noise, and

Fig. 10.7 Plans of upstairs and downstairs in an apartment. The flushing noise of an upstairs toilet was recorded on a bed downstairs (X)

dotted lines indicate the background noise. The measurement time was 5 s. The values of all factors were obtained with the integration interval of 0.5 s and the running interval of 100 ms.

As shown in Fig. 10.8a, the SPL measured by ll(0) for the flushing toilet noise was between 30 and 35 dBA, but the background noise was about 23 dBA. Thus, the maximum signal-to-noise ratio was 12 dBA. If the difference between the background noise level and the noise signal level is greater than 10 dB, the background noise does not affect significantly the noise signal measurement (Beranek, 1971). As shown in Fig. 10.8b and c, the τe value for the flushing toilet noise exceeded 100 ms with φ1 > 0.5, and τe < 0.1 ms and φ1 < 0.0.1 of the background noise throughout

Fig. 10.8 Measured factors extracted from the running ACF. Solid line indicates values for the flushing toilet noise, and dotted line indicates the background noise. (a) ll(0). (b) τe.

(c) φ1. (d) τ1. The values of all factors were obtained every 100 ms with an integration interval of 0.5 s

the measurement time. Thus, the flushing toilet noise had much more repetitive features than did the background noise. It has been reported that loudness increases in proportion to the value τe (see Section 6.4; Merthayasa and Ando, 1996). The value of τe for the flushing toilet noise was the largest near the peak of ll(0), as shown in Fig. 10.8a and b. The value of τ1 for the flushing toilet noise had a discrete value at 3.6 ms, which means that the perceived pitch was 275 Hz (Fig. 10.6d). The background noise did not have any clear pitch and tonal components, similar to white noise. These are clearly demonstrated in Fig. 10.9, which shows examples of the measured normalized ACF at t = 0.1 s, t = 0.9 s, and t = 2.5 s. The corresponding spectra are shown in Fig. 10.10. In addition, the measured special factors extracted from the IACF are shown in Fig. 10.11a–c. The IACC value for the flushing toilet

Fig. 10.9 Examples of the NACF analyzed. (a) Background noise measured at t = 0.1 s. (b and c) Flushing toilet noise measured at t = 0.9 s and 2.5 s, respectively