Evelyn M. Hoglund

Effect of intensity on sensory dissonance

Sensory dissonance is known to be related to the critical band [Greenwood (1961); Plomp and Levelt (1965)]. The maximum dissonance between two pure tones has been estimated to arise when the tones are separated by roughly 40% of a critical band [Greenwood (1991)]. Sensory dissonance disappears when the tones are separated by more than a critical band. Experimental work by Kameoka and Kuriyagawa (1969) has further demonstrated that dissonance judgments are affected by intensity. Since the size of critical bands are known to increase with increasing intensity [Moore and Glasberg (1987)], it follows that listeners should locate maximum dissonance at larger‐frequency separations for higher‐intensity tones. Similarly, the point at which dissonance disappears should involve larger frequency separation for higher intensity. The results of two experiments are reported where dissonance judgments were explicitly examined in the context of intensity‐induced changes in critical bandwidth. In the first experiment, listeners adjusted the frequency of one tone away from a fixed tone to the point of maximum dissonance. In the second experiment, listeners adjusted the tone to the point of just‐not‐noticeable dissonance. Results will be reported for 10 musician and 10 nonmusician listeners.

Telephone speech enhancement for elderly hearing‐impaired listeners

Many elderly persons with high‐frequency hearing loss find telephone use frustrating due to lower intensity levels and reductions in acoustical information that can be useful in deciphering speech. The purpose of this project is to pre‐process the speech signal before it is sent over the phone line and provide speech enhancement without the use of amplifying handsets or hearing aids at the receiving end. The enhancement technique takes into account the limited bandwidth of the phone line as well as the hearing characteristics of the user. Two pre‐processing schemes, a single channel and a double channel approach, used to increase the intelligibility of speech in these situations are discussed. The single channel method performs amplitude compression of the entire signal. The two‐channel method filters the incoming signal into high‐frequency and low‐frequency channels and performs independent compression on each before recombination. Results comparing the two speech enhancement schemes against no processin...

The effects of surgical masks on speech perception in noise

Surgical masks and blood shields worn by anesthesiologists and surgeons in hospital operating rooms may negatively impact speech communication and put patients at needless risk. Young adult subjects listened to sentences from the Speech Perception in Noise Test (SPIN) recorded by a male and female talker. All eight SPIN lists were recorded under three different speaking conditions: 1) speaking normally without any obstruction, 2) wearing a typical surgical mask, and 3) wearing a surgical mask with an attached blood shield. Multi-talker babble was mixed with the SPIN sentences at several signal-to-noise ratios to simulate conversation in noisy environments. Speaker gender and recording conditions were counterbalanced across listeners to control for learning and fatigue effects. SPIN test scores for each of the three types of recordings and both talker genders were compared in order to determine the degradation that blood-shields and surgical masks may have speech communication in the operating room. [Resea...

Auditory acuity for aircraft in real-world ambient environments

Although many psychoacoustic studies have been conducted to examine the detection of masked target sounds, the vast majority of these studies have been conducted in carefully controlled laboratory listening environments, and their results may not apply to the detection of real-world sounds in the presence of naturalistic ambient sound fields. Those studies that have examined the detection of realistic naturally-occurring sounds have been conducted in uncontrolled listening environments (i.e., outdoor listening tests) where the experimenters were unable to precisely control, or even measure, the specific characteristics of the target and masker at the time of the detection judgment. This study represents an attempt to bridge the gap between unrealistic laboratory listening studies and uncontrolled outdoor listening studies through the use of pseudorandomly-presented real world recordings of target and masking sounds. Subjects were asked to detect helicopter signals in the context of an ongoing ambient recording in a two interval detection task. The results show that the signal-to-noise ratio required to detect an aircraft sound varies across different types of ambient environments (i.e., rural, suburban, or urban).

Development and calibration of a smartphone application for use in sound mapping

Klyn and Feth (2016) reported preliminary work to use a smartphone application in a citizen-science project designed to map sound levels in Columbus, OH. Before the main project began, we discovered that the sound level measuring applications available for download had shortcomings that made them unsuitable for the proposed work. This presentation describes the development of two smartphone applications, one iOS and one Android, and the calibration procedures developed to document their accuracy and reliability. Following the suggestions of Kardous, et al. (2014, 2016), we require that the measurements be conducted using an external microphone. In use, microphone voltage is sampled for 30 seconds and processed to reflect the A-weighting scale so that sound levels are recorded as dBA values. The time and location of each sample is saved with the sound level value and can only be uploaded to the project data base if the device has been previously calibrated. Calibration stores an offset value that can be ad...

Sensitivity of pure tone versus speech-in-noise hearing screening

Adults classified as having normal hearing using conventional pure tone hearing screening often report hearing difficulties especially for situations requiring listening for speech or music in a background of noise. The purpose of this project is to compare the sensitivity of a pure tone hearing screener with a Spoken Digits in Noise test. In the first comparison, 20 young adults with normal hearing thresholds documented by a full audiometric test were asked to simulate a conductive hearing loss using an ear plug inserted into one ear. Both screeners were used to detect the simulated conductive hearing loss. In the second comparison, participants with documented mild to moderate sensorineural hearing loss were tested with both screeners. Order of testing with the screeners was counter-balanced, and the degree of hearing loss was categorized into 15 dB intervals based on their three-frequency (500, 1000, and 2000 Hz) averages and labeled Normal, Slight, Mild, or Moderate. A decision theory analysis was use...

Testing a computational model for detection of “real-world” sounds

Hoglund (et al., 2010) reported the ability of listeners to detect a recorded signal masked by nine different ambient sounds. Signals were selected from 410 recordings of two different helicopters; maskers were selected from nine outdoor field recordings from three different locations. Signal and masker levels were randomized from trial to trial in a 2I,2AFC adaptive procedure to produce psychometric functions. Signal-to-masker ratios (SNR) ranged from -22 to -4 dBA for 70% correct detections. The Hoglund et al. results were used to tune a network of non-linear oscillators to optimize its performance. To evaluate the model, recordings of three fixed-wing aircraft were obtained for use as signals in the same nine environmental backgrounds. Signal and masker recordings were pre-processed to ensure that overall RMS voltage measures reflected the sound pressure level measured in a flat-plate coupler at the headphone used by the listeners. Model predictions for complete psychometric functions were obtained bef...

Enhanced multi-channel model for auditory spectrotemporal integration

In psychoacoustics, a multi-channel model has traditionally been used to describe detection improvement for multicomponent signals. This model commonly postulates that energy or information within either the frequency or time domain is transformed into a probabilistic decision variable across the auditory channels, and that their weighted linear summation determines optimum detection performance when compared to a critical value such as a decision criterion. In this study, representative integration-based channel models, specifically focused on signal-processing properties of the auditory periphery are reviewed (e.g., Durlachs channel model). In addition, major limitations of the previous channel models are described when applied to spectral, temporal, and spectrotemporal integration performance by human listeners. Here, integration refers to detection threshold improvements as the number of brief tone bursts in a signal is increased. Previous versions of the multi-channel model underestimate listener performance in these experiments. Further, they are unable to apply a single processing unit to signals which vary simultaneously in time and frequency. Improvements to the previous channel models are proposed by considering more realistic conditions such as correlated signal responses in the auditory channels, nonlinear properties in system performance, and a peripheral processing unit operating in both time and frequency domains.

Testing a nonlinear computational channel model for masker phase effects

The masked threshold differences produced by Schroeder-phase maskers are most often attributed to the non-linear response of the normal cochlea (Summers et al., 2003). The nonlinear properties of the basilar membrane (BM) cause different response to the positive and negative Schroeder-phase maskers (i.e., + SCHR and -SCHR maskers, respectively) based on signal level, temporal synchrony, and on- and off-frequency harmonic components (Kohlrausch and Sander, 1995, Carlyon and Datta, 1997a,b, and Summers, 2000). In this study, manipulation of harmonic components of the maskers was used to explore nonlinear aspects of BM motion produced by the two different maskers. Specifically, masking period patterns (MPPs) for the + SCHR and -SCHR maskers were measured to show the influence of the phase relationships, and thus, the spectrotemporal characteristics of harmonic complexes on masking effectiveness. An enhanced channel model (Oh, 2013) provides a quantitative explanation for masking differences between + SCHR an...

Optimizing masker phase effects for use in a portable hearing screening tool

The current study is a continuation of work toward development of a preclinical indicator for noise induced hearing loss. Masked threshold differences produced by Schroeder-phase maskers have been demonstrated with long duration tones at different frequencies (1, 2, and 4 kHz) as well as with IEEE sentences (Summers and Leek, 1998) for normal hearing listeners, but these differences are not found for hearing impaired listeners. Similar results are also found for repeated short duration tone bursts and greater differences occur with systematically changed tone burst frequencies (Hoglund et al., 2012). Using the enhanced channel model (Oh, 2013), threshold differences are predicted, and the Schroeder-phase masker characteristics are adjusted to maximize the difference. This leads to a greater range of masker phase effect differences between the positive and negative Schroeder-phase maskers, and should allow greater sensitivity to preclinical hearing threshold changes. These optimized maskers were also appli...