Relationship Between Loudness Ratings and Compliance - Paper Example

The first experiment involved exploring the effects of changing frequency on the compliance level of facilitators. The results clearly show that there are differences in the compliance levels of individuals. In Participant 1, the compliance levels generally increased with the increasing overall stimulus intensity level except at 4 KHz (0 dB) (Fig. 1). The largest compliance change occurred at 1 KHz (-10 dB) + 4 kHz (-5 dB) in 0.3 sec. However, the compliance levels increased significantly at 1 KHz (0 dB) + 4 kHz (-10 dB), 1 KHz (-10 dB) + 4 kHz (0 dB), and 1 KHz (-5 dB) + 4 kHz (-5 dB). For Participant 2, the largest change occurred initially at 1 KHz (-5 dB) + 4 kHz (-5 dB), 1 KHz (-5 dB) + 4 kHz (-10 dB), and 1 KHz (-10 dB) + 4 kHz (-0 dB) when exposed to the stimulus for 0.3 seconds (Fig. 2). While the change remained high for these three frequencies, there was a significant increase in the compliance change for 1 KHz (0 dB) + 4 kHz (10 dB), 1 KHz (0 dB), and 4 kHz (0 dB). For Participant 3, overall, there is significant change for all the stimuli at various frequencies at both 0.3 seconds and 1.5 seconds (Fig. 3). Participant 4 showed a curious response to the stimulus at 1 KHz (-5 dB) + 4 kHz (-5 dB). There is also a linear increment in the compliance change against the overall stimulus intensity level at 0.3 seconds. There is also a large change for this participant at 1.5 seconds for the stimulus at different intensity levels (Fig. 4). Additionally, Participant 5 demonstrated one of the largest differences between the compliance change at 0.3 seconds and 1.5 seconds with the most significant change noted for the stimulus at 1 KHz (0 dB) + 4 kHz (-10 dB) (Fig. 5). Participant 6 shows a wide acoustic reflex threshold of between 75 and 90 dB SPL with the largest compliance change noticed in the 1 KHz (-10 dB) + 4 kHz (-5 dB).

Participant 7s compliance change was abnormally high in the 1 KHz (-5 dB) + 4 kHz (-10 dB) spectrum with also sharp changes in the 1 KHz (-5 dB) + 4 kHz (-5 dB) spectrum. The acoustic reflex threshold of all the stimuli in Participant 8 was greater than 90 dB unlike in other participants who recorded a broader spectrum between 80 dB and 100 dB. Contraction for Participant 9 occurred in the 80 100 dB spectrum with the 1 KHz (-5 dB) + 4 kHz (-5 dB) spectrum causing the biggest compliance change. Participant 10 is the first participant in which the signal at 1 KHz (0 dB) + 4 kHz (-10 dB) spectrum caused the biggest compliance change while Participant 11 is the first participant in which the signal at 1 KHz (-10 dB) + 4 kHz (0 dB) caused the largest compliance change. For Participants 12 and 13, the signal at 1 KHz (-10 dB) + 4 kHz (-5 dB) caused the largest change.

Overall, most of the respondents show higher compliance change 1 KHz (-10 dB) + 4 kHz (-5 dB) upon exposure to a 0.3 seconds stimuli. As shown in Figures 1-13, the results of this experiment are consistent with Kawase and Colleagues (1997) observation that the simultaneous presentation of facilitator enhances the magnitude of the reflex, even when the sound levels of the facilitator are considerably lower than the acoustic reflex threshold for the facilitator.

Participant No. 1:

Fig. 1. Compliance change vs. overall stimulus intensity level of Participant 1

-460375405130Participant No.2:

Fig. 2. Compliance change vs. overall stimulus intensity level of Participant 2

-11303041021000Participant No.3:

Fig. 3. Compliance change vs. overall stimulus intensity level of Participant 3

-436245377825Participant No.4:

Fig. 4. Compliance change vs. overall stimulus intensity level of Participant 4

2: Difference between both timings (0.3 sec and 1.5 sec)

There are significant timings between the two timings for the stimulus at different intensities. To most participants, the compliance change at 0.3 seconds is mainly indifferent at 4 kHz (0 dB) but the change is significantly high at 1.5 seconds. However, it represents the least change of all the stimuli. There is great variability in compliance change among the stimuli between 0.3 seconds and 1.5 seconds for all the individuals. The greatest change appears to occur as the intensity levels of all the stimuli nears 100 dB. It also appears that the sensitivity of all the participants to the stimuli at 1 KHz (-10 dB) + 4 kHz (-5 dB) decreases as the timing increases to 1.5 seconds. Participant 5 exhibited the largest compliance change of all the participants when the timing was switched from 0.3 seconds to 1.5 seconds.

-244475341630Participant No.5:

Fig. 5. Compliance change vs. overall stimulus intensity level of Participant 5

Figure 5 and Figure 6 show that the two participants did not show much change at 0.3 seconds but significantly increased at 1.5 seconds.

-304800491490Participant No.8:

Fig. 6. Compliance change vs. overall stimulus intensity level of Participant 6

-260985893445Whereas the compliance change increased as the timing increased for most participants, the opposite trend was observed for two participants (Figure 7 and Figure 8).

Figure 7. Compliance change vs. overall stimulus intensity level of Participant 12

-71755464820Participant No.13:

Figure 8. Compliance change vs. overall stimulus intensity level of Participant 13

The differences between both timings (0.3 sec and 1.5 sec) represent the variation among people about their sensitivity to different stimuli at different times of exposure. The differences in the apical vs. basal patterns of spread of excitation due to the 1 kHz signals at 0.3 seconds and 1.5 seconds may reflect the additional excitation upon exposure to the stimuli over a longer period on that frequency region (Kasawe et al., 1997).

3: Difference between each stimulus (1 + 4 kHz vs. Noise+1 kHz vs. Noise)

-181610939800

Fig. 9. 1 + 4 kHz stimuli (0.3 sec plot on left side and 1.5 sec plot on right side)

-2451103318510Fig. 10. Filtered Noise + 1 kHz stimuli (0.3 sec plot on left side and 1.5 sec plot on right side) -245110-191770

Fig. 11. Filtered Noise (0.3 sec plot on left side and 1.5 sec plot on right side

A notable difference in this study is the compliance change due to the stimulus at 4 KHz (0 dB). As it can be seen in Figure 9 above, the compliance change of this particular stimulus is little at 0.3 seconds compared to the significant change at 1.5 seconds. The decrease in change at 1 KHz (0 dB) + 4 kHz (-10 dB) in a 1 + 4 kHz, Noise+1 kHz, and Noise situation is consistent with the change discussed in the first and second sections above. There is also great variability in the compliance change for all the other stimulus frequencies at 0.3 seconds and 0.5 seconds, respectively (Fig. 9).

Figure 10 shows a finer compliance change with reduced noise. The plot shows that the compliance change reduces slightly but the optimum compliance is achieved at a much lower stimulus intensity level. This intensity level reduces further when the 1 kHz stimulus is removed and the filtered noise alone remains. The increase of the stimulus intensity results in the 1 + 4 kHz, Noise+1 kHz, and Noise situation results in the excitation of the 'tail' part of neurons which innervates the frequency region higher than the frequency of the elicitor tone (Kawase et al., 1997). According to Kawase and colleagues (1997) the spread of excited neurons may play a crucial role in eliciting the reflex.

It has been argued that a possible role of acoustically induced reflexes is to decrease the masking of responses to high-frequency sound produced by low-frequency sounds (Pang, 1988). The masking effects of one sound (signal) by another sound (masker) is thought to be asymmetrical. In other words, a high-frequency sound is much more effective in masking the response low-frequency signals and the opposite is also true (Egan and Hake, 1950). This may explain the observation that the 4Hz (0 dB) signal is highly masked by the many high frequency signals in Fig. 9 and the compliance change only become noticeable when the subject is exposed to the stimulus for a little longer.

The results above are consistent with the findings of Kasawe et al. (1997) that reported a significant correlation across subjects when the effects between I-kHz signals and the 4-kHz narrow band noises are observed. In other words, the lower the masked thresholds at the level of elicitor acoustic reflect thresholds, the lower the facilitation thresholds. Thus, the removal of the elicitor signals reduced the threshold levels of the noise signal and shifted its spectrum to 52 90 dB SPL.

4: Difference between each condition in each stimulus

As can be seen in the plots above, the presence of 4 kHz elicitor signals mask the excitation of the middle ear muscles at 1 kHz. The plots in Figure 9show that lower frequency signals (1 kHz) readily cause acoustic reflex (75-105 dB SPL). The compliance change increases with increasing intensity for 0.3 seconds. Exposure of the middle ear muscles to the stimuli for 1.5 seconds leads to contraction at the 4 kHz signal, especially as the intensity of the stimulus increases. Increased noise levels of 4 kHz signal when subjects are exposed to the stimuli for 1.5 seconds increasingly masks the 1 kHz signals. For example, the 4 kHz signal causes compliance change of the 1 KHz (-10 dB) + 4 kHz (0 dB) to decrease but causes the compliance change of 1 KHz (-5 dB) + 4 kHz (-5 dB) signal to increase.

5: Difference between each average (stimuli and time domain)

Figure 9 shows that there is great variability among stimuli at 0.3 seconds and 1.5 seconds. The compliance change increases with increasing level of stimulus intensity in both timings. The biggest difference is the compliance change of the acoustic reflex after exposure to higher frequency 4 kHz signal for 1.5 seconds at higher loudness levels. There is a significant decrease in compliance change at 1 KHz (-10 dB) + 4 kHz (-5 dB) as the stimulus intensity increase. This variability is due to the masking effect of the higher frequency signals (which become noticeable as their intensity increases) on lower frequency tones.

Relationship between Loudness ratings and compliance

Part 1: Difference between individuals/participants

The relationship between loudness and compliance change was investigated in subjects. It is known that the effects of stimulus variables such as acoustic reflex, band-width, duration, and intensity are similar in many ways to their effects on loudness. As can be seen in Figures 1-13, there is great variability between individuals as far as perception of loudness is concerned. Generally, the loudness that can cause changes in the contraction of the middle-ear-muscles falls within the loudness of 1 to 7. In Participant 1, the compliance change occurred from the subjective loudness rating of 1 and the contraction increased exponentially due to all the 1 kHz signals except for the facilitator signal at 4 kHz (0 dB). The most excitation is caused by the 1 KHz (0 dB) + 4 kHz (-10 dB) spectrum when subjected to the signal for 0.3 seconds (Fig. 1). For Participant 2, there is a sharp upward compliance change for all the signals when exposed to the signals for 0.3 seconds as shown in Fig. 2. However, the participant does not show any sign of excitation from the facilitator signal (4 kHz (0 dB)) at all.

The contraction of the middle-ear muscles of Participant 3 appear to be elicited by loudness levels ranging between 2 and 7 and increases and the loudness levels increase. The sharpest compliance change for this individual appears to be caused by the 1 KHz (-5 dB) + 4 kHz (-10 dB) while the effect of the facilitator signal loudness remains largely indifferent (Fig. 3). For Participant 4, overall, there was a slight change for all the st...