Relative contributions of specific frequency bands to the loudness of broadband sounds

Abstract

Listeners with normal hearing (NH) and sensorineural hearing loss (SNHL) were asked to compare pairs of noise stimuli and choose the louder noise in each pair. Each noise was made up of 15, two-ERB (equivalent rectangular bandwidth) wide frequency bands that varied independently over a 12-dB range from one presentation to the next. Mean levels of the bands followed the long-term average speech spectrum (LTASS) or were set to 43, 51, or 59 dB sound pressure level (SPL). The relative contribution of each band to the total loudness of the noise was determined by computing the correlation between the difference in levels for a given band on every trial and the listener's decision on that trial. Weights for SNHL listeners were governed by audibility and the spectrum of the noise stimuli, with bands near the spectral peak of the LTASS noise receiving greatest weight. NH listeners assigned greater weight to the lowest and highest bands, an effect that increased with overall level, but did not assign greater weight to bands near the LTASS peak. Additional loudness-matching and paired-comparison studies using stimuli missing one of the 15 bands showed a significant contribution by the highest band, but properties other than loudness may have contributed to the decisions.

Contribution of frequency bands to the loudness of broadband sounds: Tonal and noise stimuli

“…These levels were chosen to span the range of levels represented in the LTASS stimuli. Additional details regarding calibration can be found in Jesteadt et al (2017). The tone complex stimuli were made up of 15 sinusoids at the center frequencies of the noise bands, with mean levels equal to the mean levels of the corresponding noise bands.…”

“…A recent paper describes use of a perceptual weights paradigm to determine the relative contributions of different frequency bands to the overall loudness of broadband stimuli made up of 15 adjacent bands of noise, with either equal levels per band or band levels adjusted to approximate the longterm average speech spectrum (LTASS) (Jesteadt et al, 2017). Listeners were presented with a pair of sounds on each trial and the level of each of the 15 two-equivalent-rectangular-bandwidths (ERB) wide (Glasberg and Moore, 1990) bands was varied randomly over a range of 66 dB from one presentation to the next.…”

“…A major question in the interpretation of the data obtained by Jesteadt et al (2017) is whether listeners were basing their decisions on loudness or on some other attribute of the sounds, such as timbre or pitch. The task requires decisions concerning sounds that are similar in loudness.…”

“…The same concern applies to data obtained in loudness matching tasks. In the current study, data were obtained with both perceptual-weight and matching procedures using the 15-band noise stimuli used by Jesteadt et al (2017) and tone complexes made up of 15 tones at the center frequencies of the noise bands. The two types of stimuli sound very different and might be expected to have different timbre and pitch cues, but they produce similar results when evaluated with current loudness models (Moore, 2014;Moore et al, 1997).…”

“…All had audiometric thresholds at or below 15 dB Hearing Level (HL) at the octave audiometric frequencies. Five of the listeners had participated in an earlier study in which perceptual weights were obtained for noise stimuli (Jesteadt et al, 2017). The experimental procedures were approved by the institutional review board at the Boys Town National Research Hospital.…”