Speech level parameters in very low and excessive reverberation measured with a contact-sensor-based device and a headworn microphone.

This work deals with the effect of very low and excessive reverberation on speech sound pressure levels. Measurements were carried out in a semi-anechoic and reverberant room using a contact-sensor-based device fixed at the base of the neck and a headworn microphone placed at 2.5 cm from the speaker's mouth. Speakers produced short monologues and also described a map with the intent of correctly explaining directions to a listener 6 m away. A significant increase of about 2 dB in mean, equivalent, and mode speech levels in semi-anechoic compared to reverberant room was on average observed for the map description from recordings with the contact device, thus, highlighting an increased vocal intensity in dead rooms when the speech task had a communicative intent. Such reliable results were not found with the headworn microphone because speech levels were affected by noise recorded in the pauses. Particularly, the 30 ms logging interval brought to more severe errors in mode and mean speech levels compared to 1 s. When the pauses were removed and a logging interval of 30 ms was adopted, results were more consistent with those obtained with the contact sensor, but level differences between the two rooms still remained not significant.

Uncertainty of speech level parameters measured with a contact-sensor-based device and a headworn microphone.

This work estimates the uncertainty contributions of speech level parameters measured with a contact-sensor-based device and a headworn microphone. Four contributions are considered: (1) instrumental uncertainty, related to device calibration; (2) method repeatability and (3) reproducibility, estimated through repeated measurements without and with device repositioning, respectively; (4) source reproducibility, due to the variability of human speech. To ascertain changes in speech production, differences between measures should be at least higher than the expanded uncertainty. In the case of device repositioning, the expanded uncertainty combines contributions (1), (3), and (4). When the device is not repositioned, it combines contributions (2) and (4).

A one-school year longitudinal study of secondary school teachers' voice parameters and the influence of classroom acoustics.

Recent literature reports that a large percentage of teachers complain that teaching has an adverse effect on their voice status. Thus, more needs to be done to study their vocal behavior. The objective of this longitudinal study was twofold: to determine changes in the voice use of teachers over a school year, and to study the relationships between voice use and classroom acoustic parameters. Thirty-one teachers from two secondary schools in Turin (Italy) were involved at the beginning of the 2014-2015 school year, and 22 of them also participated at the end of the same school year. The results show that teachers adjust their voices with noise and reverberation. A minimum value of the sound pressure level of voice (SPL) was found at a mid-frequency reverberation time of 0.8 s in both periods. Moreover, the teachers who worked in the worst classroom acoustic conditions showed an increase of 2.3 dB in the mean SPL and a decrease of 10% in the voicing time percentage at the end of the school year. A predictive model that can be used to estimate the mean SPL from the background noise level and the reverberation time, based on collected data, is here proposed.

Intra-speaker and inter-speaker variability in speech sound pressure level across repeated readings.

The intra- and inter-speaker variability of speech sound pressure level (SPL) has been investigated under repeatability conditions in this work. In a semi-anechoic chamber, speech from 17 individuals was recorded with a sound level meter, a headworn microphone, and a vocal monitoring device. The subjects were asked to read twice and in sequence two phonetically balanced passages. The speech variability has been investigated for mean, equivalent, and mode SPL from each reading and device. The intra-speaker variability has been evaluated by means of the average among individual standard deviations in the four readings and it reached the maximum of 2 dB for mode SPL. For the inter-speaker variability, the experimental standard deviation of individual averaged SPL parameters among the four repeated measures has been calculated, obtaining the highest value of 5.3 dB for mode SPL. Changes in SPL variability have been evaluated with different logging intervals for each device. The influence of speech material has been investigated by the Wilcoxon test on paired lists of descriptive statistics for SPL distribution and equivalent SPL in the repeated readings. The data reported in this study may be considered as a preliminary reference for the investigation of changes in speech SPL over subjects.