Asymmetric visual capture of virtual sound sources in the distance dimension.

Visual capture describes the tendency of a sound to be mislocalized to the location of a plausible visual target. This effect, also known as the ventriloquist effect, has been extensively studied in humans, but primarily for mismatches in the angular direction between auditory and visual targets. Here, visual capture was examined in the distance dimension using a single visual target (an un-energized loudspeaker) and invisible virtual sound sources presented over headphones.

The impact of head-related impulse response delay treatment strategy on psychoacoustic cue reconstruction errors from virtual loudspeaker arrays.

Known errors exist in loudspeaker array processing techniques, often degrading source localization and timbre. The goal of the present study was to use virtual loudspeaker arrays to investigate how treatment of the interaural time delay (ITD) cue from each loudspeaker impacts these errors. Virtual loudspeaker arrays rendered over headphones using head-related impulse responses (HRIRs) allow flexible control of array size.

Reverberation Degrades Pitch Perception but Not Mandarin Tone and Vowel Recognition of Cochlear Implant Users.

Objectives: The primary goal of this study was to investigate the effects of reverberation on Mandarin tone and vowel recognition of cochlear implant (CI) users and normal-hearing (NH) listeners. To understand the performance of Mandarin tone recognition, this study also measured participants' pitch perception and the availability of temporal envelope cues in reverberation.

Design: Fifteen CI users and nine NH listeners, all Mandarin speakers, were asked to recognize Mandarin single-vowels produced in four lexical tones and rank harmonic complex tones in pitch with different reverberation times (RTs) from 0 to 1 second.

Reverberation strength perceived by normal-hearing listeners predictable based on time-varying binaural loudness.

Previous work has explored novel binaural combinations of reverberation and the resulting perceived reverberation strength (reverberance). The present study examines the perceptual effects of additional binaural combinations of reverberation with the goal of explaining reverberance in terms of basic psychoacoustic principles. Stimuli were generated using virtual space techniques simulating a speech source 3 m to the listener's right in a moderately reverberant environment.

Associations between speech recognition at high levels, the middle ear muscle reflex and noise exposure in individuals with normal audiograms.

It has been hypothesized that noise-induced cochlear synaptopathy in humans may result in functional deficits such as a weakened middle ear muscle reflex (MEMR) and degraded speech perception in complex environments. Although relationships between noise-induced synaptic loss and the MEMR have been demonstrated in animals, effects of noise exposure on the MEMR have not been observed in humans. The hypothesized relationship between noise exposure and speech perception has also been difficult to demonstrate conclusively.

Sensitivity to Interaural Phase in Older Hearing-Impaired Listeners Correlates With Nonauditory Trail Making Scores and With a Spatial Auditory Task of Unrelated Peripheral Origin.

Interaural phase difference (IPD) discrimination upper frequency limits and just-noticeable differences (JNDs), interaural level difference (ILD) JNDs, and diotic intensity JNDs were measured for 20 older hearing-impaired listeners with matched moderate sloping to severe sensorineural hearing losses. The JNDs were measured using tone stimuli at 500 Hz. In addition to these auditory tests, the participants completed a cognitive test (Trail Making Test).

Interactions Between Digital Noise Reduction and Reverberation: Acoustic and Behavioral Effects.

Background: Digital noise reduction (DNR) processing is used in hearing aids to enhance perception in noise by classifying and suppressing the noise acoustics. However, the efficacy of DNR processing is not known under reverberant conditions where the speech-in-noise acoustics are further degraded by reverberation.

Purpose: The purpose of this study was to investigate acoustic and perceptual effects of DNR processing across a range of reverberant conditions for individuals with hearing impairment.

A dissociation between speech understanding and perceived reverberation.

As direct-to-reverberant energy ratio (DRR) decreases or decay time increases, speech intelligibility tends to decrease for both normal-hearing and hearing-impaired listeners. Given this relationship, it is easy to assume that perceived reverberation (reverberance) would act as an intermediary-as physical reverberation increases, so does reverberance, and speech intelligibility decreases as a result. This assumption has not been tested explicitly.

Effects of Reverberation on the Relation Between Compression Speed and Working Memory for Speech-in-Noise Perception.

Objectives: Previous study has suggested that when listening in modulated noise, individuals benefit from different wide dynamic range compression (WDRC) speeds depending on their working memory ability. Reverberation reduces the modulation depth of signals and may impact the relation between WDRC speed and working memory. The purpose of this study was to examine this relation across a range of reverberant conditions.

Speech intelligibility in rooms: Disrupting the effect of prior listening exposure.

It has been demonstrated that prior listening exposure to reverberant environments can improve speech understanding in that environment. Previous studies have shown that the buildup of this effect is brief (less than 1 s) and seems largely to be elicited by exposure to the temporal modulation characteristics of the room environment. Situations that might be expected to cause a disruption in this process have yet to be demonstrated.

Effects of reverberation, background talker number, and compression release time on signal-to-noise ratio.

Wide dynamic range compression (WDRC) processing in hearing aids alters the signal-to-noise ratio (SNR) of a speech-in-noise signal. This effect depends on the modulations of the speech and noise, input SNR, and WDRC speed. The purpose of the present experiment was to examine the change in output SNR caused by the interaction between modulation characteristics and WDRC speed.

Speech perception adjusts to stable spectrotemporal properties of the listening environment.

When perceiving speech, listeners compensate for reverberation and stable spectral peaks in the speech signal. Despite natural listening conditions usually adding both reverberation and spectral coloration, these processes have only been studied separately. Reverberation smears spectral peaks across time, which is predicted to increase listeners' compensation for these peaks.

Speech intelligibility in rooms: Effect of prior listening exposure interacts with room acoustics.

There is now converging evidence that a brief period of prior listening exposure to a reverberant room can influence speech understanding in that environment. Although the effect appears to depend critically on the amplitude modulation characteristic of the speech signal reaching the ear, the extent to which the effect may be influenced by room acoustics has not been thoroughly evaluated. This study seeks to fill this gap in knowledge by testing the effect of prior listening exposure or listening context on speech understanding in five different simulated sound fields, ranging from anechoic space to a room with broadband reverberation time (T60) of approximately 3 s.

Auditory distance perception in humans: a review of cues, development, neuronal bases, and effects of sensory loss.

Auditory distance perception plays a major role in spatial awareness, enabling location of objects and avoidance of obstacles in the environment. However, it remains under-researched relative to studies of the directional aspect of sound localization. This review focuses on the following four aspects of auditory distance perception: cue processing, development, consequences of visual and auditory loss, and neurological bases.

Auditory distance coding in rabbit midbrain neurons and human perception: monaural amplitude modulation depth as a cue.

Mechanisms underlying sound source distance localization are not well understood. Here we tested the hypothesis that a novel mechanism can create monaural distance sensitivity: a combination of auditory midbrain neurons' sensitivity to amplitude modulation (AM) depth and distance-dependent loss of AM in reverberation. We used virtual auditory space (VAS) methods for sounds at various distances in anechoic and reverberant environments.

Near-field discrimination of sound source distance in the rabbit.

The acoustical cues and physiological processing mechanisms underlying the perception of the distance of sound sources are not well understood. To understand the relation between physiology and behavior, a first step is to use an animal model to study distance sensitivity. The goal of these experiments was to establish the capacity of the Dutch-belted rabbit to discriminate between sound sources at two distances.

Auditory/visual distance estimation: accuracy and variability.

Past research has shown that auditory distance estimation improves when listeners are given the opportunity to see all possible sound sources when compared to no visual input. It has also been established that distance estimation is more accurate in vision than in audition. The present study investigates the degree to which auditory distance estimation is improved when matched with a congruent visual stimulus.

Enhancement of speech intelligibility in reverberant rooms: role of amplitude envelope and temporal fine structure.

The temporal envelope and fine structure of speech make distinct contributions to the perception of speech in normal-hearing listeners, and are differentially affected by room reverberation. Previous work has demonstrated enhanced speech intelligibility in reverberant rooms when prior exposure to the room was provided. Here, the relative contributions of envelope and fine structure cues to this intelligibility enhancement were tested using an open-set speech corpus and virtual auditory space techniques to independently manipulate the speech cues within a simulated room.

Amplitude modulation detection by human listeners in reverberant sound fields: Effects of prior listening exposure.

Previous work [Zahorik et al., POMA, 15, 050002 (2012)] has reported that for both broadband and narrowband noise carrier signals in a simulated reverberant sound field, human sensitivity to amplitude modulation (AM) is higher than would be predicted based on the acoustical modulation transfer function (MTF) of the listening environment. These results may be suggestive of mechanisms that functionally enhance modulation in reverberant listening, although many details of this enhancement effect are unknown.

Time course of a perceptual enhancement effect for noise-masked speech in reverberant environments.

Speech intelligibility has been shown to improve with prior exposure to a reverberant room environment [Brandewie and Zahorik (2010). J. Acoust.

Amplitude modulation detection by human listeners in reverberant sound fields: Carrier bandwidth effects and binaural versus monaural comparison.

Previous work [Zahorik et al., POMA, 12, 050005 (2011)] has reported that for a broadband noise carrier signal in a simulated reverberant sound field, human sensitivity to amplitude modulation (AM) is higher than would be predicted based on the broadband acoustical modulation transfer function (MTF) of the listening environment. Interpretation of this result was complicated by the fact that acoustical MTFs of rooms are often quite different for different carrier frequency regions, and listeners may have selectively responded to advantageous carrier frequency regions where the effective acoustic modulation loss due to the room was less than indicated by a broadband acoustic MTF analysis.

Prior listening exposure to a reverberant room improves open-set intelligibility of high-variability sentences.

Previous studies have demonstrated that speech understanding in reverberant rooms improves when listeners are given prior exposure to the room. Results from these room-adaptation studies are limited, however, because they were conducted with materials that are not representative of the high acoustic variability observed in speech signals during everyday communication. Here, room adaptation effects were measured using an open-set speech corpus with high lexical and indexical variability and virtual auditory space techniques to simulate binaural listening in rooms.

Amplitude modulation detection by human listeners in sound fields.

The temporal modulation transfer function (TMTF) approach allows techniques from linear systems analysis to be used to predict how the auditory system will respond to arbitrary patterns of amplitude modulation (AM). Although this approach forms the basis for a standard method of predicting speech intelligibility based on estimates of the acoustical modulation transfer function (MTF) between source and receiver, human sensitivity to AM as characterized by the TMTF has not been extensively studied under realistic listening conditions, such as in reverberant sound fields. Here, TMTFs (octave bands from 2 - 512 Hz) were obtained in 3 listening conditions simulated using virtual auditory space techniques: diotic, anechoic sound field, reverberant room sound field.

Phonemic restoration effect reversed in a reverberant room.

Classic demonstrations of the phonemic restoration effect show increased intelligibility of interrupted speech when the interruptions are caused by a plausible masking sound rather than by silent periods. Previous studies of this effect have been conducted exclusively under anechoic or nearly anechoic listening conditions. This study demonstrates that the effect is reversed when sounds are presented in a realistically simulated reverberant room (broadband T(60) = 1.