Michael F Dorman

Michael F Dorman
Arizona State University | ASU · Department of Speech and Hearing Science

Ph.D.

About

255
Publications
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Publications

Publications (255)
Article
The AzBio sentence test is widely used to assess speech perception pre- and post-cochlear implantation. This study created and validated a Hebrew version of AzBio (HeBio) and tested its intelligibility amidst background noise. In Experiment 1, 1,000 recorded Hebrew sentences were presented via five-channel vocoder to 10 normal hearing (NH) listene...
Article
Full-text available
Patients fit with cochlear implants (CIs) commonly indicate at the time of device fitting and for some time after, that the speech signal sounds abnormal. A high pitch or timbre is one component of the abnormal percept. In this project, our aim was to determine whether a number of years of CI use reduced perceived upshifts in frequency spectrum and...
Article
Purpose For bilaterally implanted patients, the automatic gain control (AGC) in both left and right cochlear implant (CI) processors is usually neither linked nor synchronized. At high AGC compression ratios, this lack of coordination between the two processors can distort interaural level differences, the only useful interaural difference cue avai...
Article
Objective: To create and validate a Spanish sentence test for evaluation of speech understanding of Spanish-speaking listeners with hearing loss or cochlear implants (CI). Study design: Two thousand sentences were recorded from two male and two female speakers. The average intelligibility of each sentence was estimated as the mean score achieved...
Article
Background Both the Roger remote microphone and on-ear, adaptive beamforming technologies (e.g., Phonak UltraZoom) have been shown to improve speech understanding in noise for cochlear implant (CI) listeners when tested in audio-only (A-only) test environments. Purpose Our aim was to determine if adult and pediatric CI recipients benefited from the...
Article
Objectives: We investigated the ability of single-sided deaf listeners implanted with a cochlear implant (SSD-CI) to (1) determine the front-back and left-right location of sound sources presented from loudspeakers surrounding the listener and (2) use small head rotations to further improve their localization performance. The resulting behavioral...
Article
Background Previous research has found that when the location of a talker was varied and an auditory prompt indicated the location of the talker, the addition of visual information produced a significant and large improvement in speech understanding for listeners with bilateral cochlear implants (CIs) but not with a unilateral CI. Presumably, the s...
Article
A review of data published or presented by the authors from two populations of subjects (normal hearing listeners and patients fit with cochlear implants, CIs) involving research on sound source localization when listeners move is provided. The overall theme of the review is that sound source localization requires an integration of auditory-spatial...
Article
Full-text available
Fourteen single-sided deaf listeners fit with an MED-EL cochlear implant (CI) judged the similarity of clean signals presented to their CI and modified signals presented to their normal-hearing ear. The signals to the normal-hearing ear were created by (a) filtering, (b) spectral smearing, (c) changing overall fundamental frequency (F0), (d) F0 con...
Article
Objective: Our aim was to determine the effect of acute changes in cochlear place of stimulation on cochlear implant (CI) sound quality. Design: In Experiment 1, 5 single-sided deaf (SSD) listeners fitted with a long (28-mm) electrode array were tested. Basal shifts in place of stimulation were implemented by turning off the most apical electrod...
Article
Full-text available
Purpose There is a growing body of literature that suggests a linkage between impaired auditory function, increased listening effort, and fatigue in children and adults with hearing loss. Research suggests this linkage may be associated with hearing loss–related variations in diurnal cortisol levels. Here, we examine variations in cortisol profiles...
Article
Purpose Our aim was to make audible for normal-hearing listeners the Mickey Mouse™ sound quality of cochlear implants (CIs) often found following device activation. Method The listeners were 3 single-sided deaf patients fit with a CI and who had 6 months or less of CI experience. Computed tomography imaging established the location of each electro...
Article
Full-text available
The modern cochlear implant (CI) is the most successful neural prosthesis developed to date. CIs provide hearing to the profoundly hearing impaired and allow the acquisition of spoken language in children born deaf. Results from studies enabled by the CI have provided new insights into (a) minimal representations at the periphery for speech recepti...
Article
Full-text available
Objective: To evaluate outcomes in pediatric and adolescent patients with single-sided deafness (SSD) undergoing cochlear implantation. Methods: A retrospective cohort design at two tertiary level academic cochlear implant centers. The subjects included nine children ages 1.5 to 15 years-old with single-sided deafness (SSD) who had undergone cochle...
Article
Unilateral severe-to-profound sensorineural hearing loss (SNHL), also known as single sided deafness (SSD), is a problem that affects both children and adults, and can have severe and detrimental effects on multiple aspects of life including music appreciation, speech understanding in noise, speech and language acquisition, performance in the class...
Article
Objective: Our primary aim was to determine, in a simulation of a crowded restaurant, the value to speech understanding of (i) a unilateral cochlear implant (CI), (ii) a CI plus CROS (contralateral routing of signals) aid system and (iii) bilateral CIs when tested with and without beamforming microphones. Design: The listeners were 7 CI listeners w...
Article
Background: When cochlear implant (CI) listeners use a directional microphone or beamformer system to improve speech understanding in noise, the gain in understanding for speech presented from the front of the listener coexists with a decrease in speech understanding from the back. One way to maximize the usefulness of these systems is to keep a m...
Article
Objective: The objectives of this study were to assess the effectiveness of various measures of speech understanding in distinguishing performance differences between adult bimodal and bilateral cochlear implant (CI) recipients and to provide a preliminary evidence-based tool guiding clinical decisions regarding bilateral CI candidacy. Design: T...
Article
Purpose: The primary purpose of this study was to assess speech understanding in quiet and in diffuse noise for adult cochlear implant (CI) recipients utilizing bimodal hearing or bilateral CIs. Our primary hypothesis was that bilateral CI recipients would demonstrate less effect of source azimuth in the bilateral CI condition due to symmetric int...
Article
Objectives: We report on the ability of patients fit with bilateral cochlear implants (CIs) to distinguish the front-back location of sound sources both with and without head movements. At issue was (i) whether CI patients are more prone to front-back confusions than normal hearing listeners for wideband, high-frequency stimuli; and (ii) if CI pat...
Article
Purpose: The aim of this article is to summarize recent published and unpublished research from our 2 laboratories on improving speech understanding in complex listening environments by listeners fit with cochlear implants (CIs). Method: CI listeners were tested in 2 listening environments. One was a simulation of a restaurant with multiple, dif...
Article
Objective: The goal of the present study was to assess the sound quality of a cochlear implant for single-sided deaf (SSD) patients fit with a cochlear implant (CI). Background: One of the fundamental, unanswered questions in CI research is "what does an implant sound like?" Conventional CI patients must use the memory of a clean signal, often d...
Article
Purpose: The aim of this experiment was to compare, for patients with cochlear implants (CIs), the improvement for speech understanding in noise provided by a monaural adaptive beamformer and for two interventions that produced bilateral input (i.e., bilateral CIs and hearing preservation [HP] surgery). Method: Speech understanding scores for se...
Article
The SilverMedal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
Article
Background: Sentence understanding scores for patients with cochlear implants (CIs) when tested in quiet are relatively high. However, sentence understanding scores for patients with CIs plummet with the addition of noise. Purpose: To assess, for patients with CIs (MED-EL), (1) the value to speech understanding of two new, noise-reducing microph...
Article
Full-text available
Purpose: Five experiments probed auditory-visual (AV) understanding of sentences by users of cochlear implants (CIs). Method: Sentence material was presented in auditory (A), visual (V), and AV test conditions to listeners with normal hearing and CI users. Results: (a) Most CI users report that most of the time, they have access to both A and...
Chapter
The design and performance of the present-day cochlear implants are described. In broad terms, the design principles now in use include (1) representing at least most of the information that can be perceived according to place, frequency, and intensity of stimulation; (2) not making any assumptions about sounds in the environment or in particular h...
Book
N.M. Young, K. Iler Kirk (Eds.) Pediatric Cochlear Implantation ▶ Educates clinicians in the field of pediatric cochlear im-plantation as to the current and emerging best practices ▶ Expands upon the current literature regarding the role of cognition and executive function in pediatric cochlear implant outcomes ▶ Aimed at neurotologists and pediatr...
Article
Purpose: To assess the role of interaural time differences and interaural level differences in (a) sound-source localization, and (b) speech understanding in a cocktail party listening environment for listeners with bilateral cochlear implants (CIs) and for listeners with hearing-preservation CIs. Methods: Eleven bilateral listeners with MED-EL...
Article
Objective: Our primary aim was to determine whether listeners in the following patient groups achieve localization accuracy within the 95th percentile of accuracy shown by younger or older normal-hearing (NH) listeners: (1) hearing impaired with bilateral hearing aids, (2) bimodal cochlear implant (CI), (3) bilateral CI, (4) hearing preservation C...
Article
Full-text available
Hypothesis: The purpose of this study was to examine changes in cortical development and neuroplasticity in a child with single-sided deafness (SSD) before and after cochlear implantation (CI). Background: The extent to which sensory pathways reorganize in childhood SSD is not well understood and there is currently little evidence demonstrating...
Article
Full-text available
Objective: To assess improvements in sound source localization and speech understanding in complex listening environments after unilateral cochlear implantation for single-sided deafness (SSD). Study design: Nonrandomized, open, prospective case series. Setting: Tertiary referral center. Patients: Nine subjects with a unilateral cochlear imp...
Article
To compare speech understanding with bimodal hearing and bilateral cochlear implants (CIs). Within-subjects, repeated-measures. Speech understanding was assessed in the following conditions: unilateral hearing aid (HA) in the non-implanted ear, unilateral CI, bimodal (CI + HA), and bilateral CI. In addition, three participants had bilateral hearing...
Patent
Full-text available
A hearing assistive device is provided having a microphone, at least one audio signal processing mechanism, a vibration signal processing mechanism, and a vibrator. The audio signal processing mechanism receives an input audio signal from the microphone and generates a first output signal according to the received input audio signal wherein the fir...
Article
Full-text available
The cochlear implant has provided the first substantial restoration of a human sense by a medical intervention. This accomplishment was brought about by the efforts, over a 50+ year period, of many individuals in laboratories around the world. In this paper, we recount the history of one of the early projects - the Utah Artificial Ear project. In 1...
Article
Full-text available
In this report, we used filtered noise bands to constrain listeners' access to interaural level differences (ILDs) and interaural time differences (ITDs) in a sound source localization task. The samples of interest were listeners with single-sided deafness (SSD) who had been fit with a cochlear implant in the deafened ear (SSD-CI). The comparison s...
Article
Full-text available
The aim of this article was to study sound source localization by cochlear implant (CI) listeners with low-frequency (LF) acoustic hearing in both the operated ear and in the contralateral ear. Eight CI listeners had symmetrical LF acoustic hearing and 4 had asymmetrical LF acoustic hearing. The effects of two variables were assessed: (i) the symme...
Article
Speech understanding was assessed in a simulated restaurant and cocktail party environment for 39 adult cochlear implant recipients (18 bilateral, 21 hearing preservation). Speech was presented as either collocated (S0N0) or spatially separated from the noise (S0N0-360 or S0N90&270). We calculated the benefit of adding a second CI, acoustic hearing...
Article
The history of cochlear implants can be divided into four stages. The first, in the early 1960s, was the period of the pioneers (e.g., House, Doyle, and Simmons) who found minimal interest, even distain, from others for their work. The second stage, in the 1970s, saw a worldwide proliferation of groups who designed devices with multiple sites of co...
Article
Starting about 10 years ago in Europe, patients who had one normally hearing ear and one deafened ear were fitted with cochlear implants in an effort to suppress tinnitus in the deafened ear. That effort was very successful. More recently, single sided deaf patients without tinnitus have been implanted in an effort to improve health-related quality...
Article
Objectives: The aims of this study were (i) to determine the magnitude of the interaural level differences (ILDs) that remain after cochlear implant (CI) signal processing and (ii) to relate the ILDs to the pattern of errors for sound source localization on the horizontal plane. Design: The listeners were 16 bilateral CI patients fitted with MED...
Article
Full-text available
The aim of this project was to determine for bimodal cochlear implant (CI) patients, i.e. patients with low-frequency hearing in the ear contralateral to the implant, how speech understanding varies as a function of the difference in level between the CI signal and the acoustic signal. The data suggest that (1) acoustic signals perceived as signifi...
Article
Objective: The aims of this study were to (1) detect the presence and edge frequency (fe) of a cochlear dead region in the ear with residual acoustic hearing for bimodal cochlear implant users, and (2) determine whether amplification based on the presence or absence of a dead region would improve speech understanding and sound quality. Design: T...
Article
The purpose of this study was to investigate horizontal plane localization and interaural time difference (ITD) thresholds for 14 adult cochlear implant recipients with hearing preservation in the implanted ear. Localization to broadband noise was assessed in an anechoic chamber with a 33-loudspeaker array extending from -90 to +90 degrees. Three l...
Article
The purpose of this study was to examine the availability of binaural cues for adult, bilateral cochlear implant (CI) patients, bimodal patients and hearing preservation patients using a multiple-baseline, observational study design. Speech recognition was assessed using the Bamford-Kowal-Bench Speech-in-Noise (BKB-SIN) test as well as the AzBio se...
Article
In English, most word-initial syllables are stressed. Listeners use these syllable strength cues to identify word boundaries in degraded acoustic conditions. This is evident in the types of lexical boundary errors they make when tasked with parsing a continuous stream of degraded speech: word boundaries are more often inserted before strong syllabl...
Article
The present research asks whether two tactile aids with directional microphones, by providing additional inter-channel level information and etc., could help unilateral cochlear implant (CI) localize sound sources. For normal hearing subjects, sound source localization based on tactile vibration cues alone can be as accurate as auditory localizatio...
Article
Full-text available
Cochlear implant (CI) users have shown benefit from residual low-frequency hearing in the contra-lateral ear (Dorman and Gifford, 2010). One source of this benefit is the enhancement of cues important for identifying word boundaries (Spitzer et al., 2009). However, there are a large number of CI users who do not have residual hearing, but who could...
Article
Several measures of sound source localization performance of 45 listeners with normal hearing were obtained when loudspeakers were in the front hemifield. Localization performance was not statistically affected by filtering the 200-ms, 2-octave or wider noise bursts (125 to 500, 1500 to 6000, and 125 to 6000 Hz wide noise bursts). This implies that...
Article
Objective: The aim of this study was to assess the benefit of having preserved acoustic hearing in the implanted ear for speech recognition in complex listening environments. Design: The present study included a within-subjects, repeated-measures design including 21 English-speaking and 17 Polish-speaking cochlear implant (CI) recipients with pr...
Article
Full-text available
In a previous paper we reported the frequency selectivity, temporal resolution, nonlinear cochlear processing, and speech recognition in quiet and in noise for 5 listeners with normal hearing (mean age 24.2 years) and 17 older listeners (mean age 68.5 years) with bilateral, mild sloping to profound sensory hearing loss (Gifford et al., 2007). Since...
Article
Objectives: The authors describe the localization and speech-understanding abilities of a patient fit with bilateral cochlear implants (CIs) for whom acoustic low-frequency hearing was preserved in both cochleae. Design: Three signals were used in the localization experiments: low-pass, high-pass, and wideband noise. Speech understanding was ass...
Article
Objectives: Patients with a cochlear implant (CI) in one ear and a hearing aid in the other ear commonly achieve the highest speech-understanding scores when they have access to both electrically and acoustically stimulated information. At issue in this study was whether a measure of auditory function in the hearing aided ear would predict the ben...
Article
Full-text available
In this article we review, and discuss the clinical implications of, five projects currently underway in the Cochlear Implant Laboratory at Arizona State University. The projects are (1) norming the AzBio sentence test, (2) comparing the performance of bilateral and bimodal cochlear implant (CI) patients in realistic listening environments, (3) acc...
Article
The first cochlear implant surgery was performed over 50 years ago and allowed a patient to hear "sounds." Today, professionals expect high levels of speech understanding for adults who are postlingually deaf and who receive a cochlear implant, and for children who are congenitally deaf-if the children receive a cochlear implant early and if they r...
Article
: It was hypothesized that auditory training would allow bimodal patients to combine in a better manner the low-frequency acoustic information provided by a hearing aid with the electric information provided by a cochlear implant, thus maximizing the benefit of combining acoustic (A) and electric (E) stimulation (EAS). : Performance in quiet or in...
Article
Full-text available
This paper provides a review of the current literature on psychophysical properties of low-frequency hearing, both before and after implantation, with a focus on frequency selectivity, nonlinear cochlear processing, and speech perception in temporally modulated maskers for bimodal listeners as well as patients with hearing preservation in the impla...
Article
Background: Both bilateral cochlear implants (CIs) and bimodal (electric plus contralateral acoustic) stimulation can provide better speech intelligibility than a single CI. In both cases patients need to combine information from two ears into a single percept. In this paper we ask whether the physiological and psychological processes associated w...
Article
Full-text available
Both bilateral cochlear implants (CIs) and bimodal (electric plus contralateral acoustic) stimulation can provide better speech intelligibility than a single CI. In both cases patients need to combine information from two ears into a single percept. In this paper we ask whether the physiological and psychological processes associated with aging alt...
Article
The cochlear implant (CI) is one of the great success stories of modern medicine. A high level of function is provided for most patients. However, some patients still do not achieve excellent or even good results using the present-day devices. Accumulating evidence is pointing to differences in the processing abilities of the "auditory brain" among...
Chapter
Full-text available
Cortical development is dependent on both intrinsic and extrinsic (stimulus-driven) factors. The absence of sensory input from birth, as in congenital deafness, inhibits the normal growth and connectivity needed to form a functional sensory system, resulting in deficits in spoken language. Cochlear implants (CIs) bypass peripheral cochlear damage,...
Article
The goal of this study was to create and validate a new set of sentence lists that could be used to evaluate the speech perception abilities of hearing-impaired listeners and cochlear implant (CI) users. Our intention was to generate a large number of sentence lists with an equivalent level of difficulty for the evaluation of performance over time...
Article
Adult patients with bilateral cochlear implants report a significant gain in health-related quality of life relative to having a single cochlear implant. Gains are found in multiple domainsin this article, we focus on hearing and speech understanding. There are several factors that likely contribute to the hearing-related gain in quality of life. T...
Article
thresholds observed at 0.25 and 0.50 peaks/octave (Saoji et al., 2009). The bandwidth and audio-frequency range of the noise band carrier has little effect on SMD thresholds of NH listeners. That is, sensitivity to 1cycle/octave modulation obtained to a four-octave noiseband is not likely different than that obtained to a one-octave noiseband teste...
Article
Distorted vowel production is a hallmark characteristic of dysarthric speech and often is characterized by spectral and temporal degradation, flattening of spectral change formants, and vowel space distortions that may differentially affect high versus low or front versus back contrasts. Because acoustic information critical to accurate speech perc...
Article
Full-text available
The majority of recently implanted, cochlear implant patients can potentially benefit from a hearing aid in the ear contralateral to the implant. When patients combine electric and acoustic stimulation, word recognition in quiet and sentence recognition in noise increase significantly. Several studies suggest that the acoustic information that lead...
Article
Full-text available
Children who experience long periods of auditory deprivation are susceptible to large-scale reorganization of auditory cortical areas responsible for the perception of speech and language. One consequence of this reorganization is that integration of combined auditory and visual information may be altered after hearing is restored with a cochlear i...
Article
The primary objective of this study was to determine whether a revision and/or expansion of current audiologic cochlear implant candidacy criteria is warranted. The study design was a retrospective review of postoperative speech perception performance for 22 adult cochlear implant recipients who demonstrated preoperative Consonant Nucleus Consonant...