# Listeners' Spectral Reallocation Preferences for Speech in Noise
## 4 Expt. 2: Spectral Reallocation Preferences for Band-Limited Speech
### Results  
#### 4.3.1 Preferences  
Figure 5 shows mean listener preferences at the end of the adjustment phase, intelligibility scores in the test phase, and the time spent in the adjustment phase, for the quiet and masked presentation conditions. For each of the four features, listeners' preferences indicate a clear effect of increasing masker level. For the LP feature, listeners chose a cut-off frequency of around 3 kHz in quiet but raised the cut-off frequency to increasingly higher frequencies as the SNR decreased. Listeners also raised the cut-off frequency in the HP condition, from a value of around 700 Hz in quiet to around 1 kHz in noise. As a consequence, listeners chose to transfer energy from the sub-1 kHz to the region above 1 kHz. A similar preference for high frequencies is seen in the CF condition, in which listeners shifted the octave band of speech from a centre frequency of around 1.5 kHz in quiet to a value close to 2.5 kHz in noise. In the condition where listeners were able to choose the bandwidth of speech, a mild increase from 3.25 octaves in quiet to 3.45 octaves in the \(-6\) dB SNR condition was observed. However, this increase is not statistically significant (see below).  
Unlike in Expt. 1, none of the adjustment options open to listeners in Expt. 2 corresponded to the original speech, since in all cases the bandwidth of speech was restricted. Listeners might have been expected to choose the adjustment value that led to the widest speech band in the quiet condition but this was not the case (see Section 4.4 below). For the  
Figure 5: **(Left)**: Listeners’ preferred adjustments; **(middle)**: keyword identification rates; **(right)**: adjustment times for the four modifications of Expt. 2. Details as for Figure 2.  
LP condition, the mean preferred cut-off of 3 kHz is substantially lower than the 5.4 kHz cut-off that would have led to the widest band of speech; likewise, for high-pass filtering, the chosen value of just above 700 Hz is well above the 450 Hz value that produces the widest band. A similar outcome is present in the BW condition, where listeners were able to choose a 4.58 octave band but instead preferred a bandwidth closer to 3.25 octaves on average. The notion of the widest band is less straightforward in the CF case since all bands were 1 octave wide; in terms of linear Hz bandwidth, the highest cut-off frequency (5.09 kHz) produced the widest band but presumably listeners were also sensitive to optimising the location in the frequency of this band, resulting in a choice of around 1.5 kHz in the quiet condition.  
Kruskal-Wallis H tests were conducted to compare the effect of SNR on preferences for each of the four features, indicating significant effects for LP, HP and CF conditions (min \(H=43.3\), \(p<0.001\)) but not for BW (\(H=6.2\), \(p=0.10\)). Post hoc tests suggest that all pairs of SNRs differed at the \(p=0.05\) level, except for the following: preferences in the \(-6\) and \(-3\) dB conditions were identical (\(p=0.23\)) in the LP condition; for the HP condition, the masked conditions did not differ statistically (min \(p=0.25\)) but all differed from the quiet condition.