Prediction of contextual speech intelligibility from isolated word intelligibility measures

The purpose of this study was to evaluate the efficacy of two nonlinear formulae posited by Boothroyd (1978) for prediction of contextual intelligibility from measures of isolated word intelligibility with four different sets of speech intelligibility data. Both of Boothroyd's formulae, Pc = 1 - (1 - Pi)2 and Pc = 1 - (1 - Pi)1.5 (1 + Pi), provided excellent fit of measured contextual intelligibility with predicted contextual intelligibility for all sets of data. Attempts to improve correlation coefficients between measured and predicted contextual intelligibility by iterating Boothroyd's suggested exponents did not significantly improve the predictive ability of the original formulae.     

Relations between speech intelligibility and psychoacoustical modulation transfer function (PMTF)

The modulation transfer function, MTF, has proved to be a powerful measure for predicting speech intelligibility in speech transmission channels. We extended it to include the ear, by measuring the psycho-acoustical MTF, i.e. the PMTF. Tone thresholds of 11 normal-hearing and 20 hearing-impaired subjects were measured in presence of unmodulated and intensity modulated noise. Octave frequencies from 500 to 4,000 Hz were used. The noise was octave filtered around the frequency of the probe tone. Six modulation frequencies from 1 to 50 Hz were used. From these results the PMTFs were calculated, as well as the corresponding psycho-acoustical speech transmission indices, i.e. the PSTIs. The subjects' speech discrimination scores in quiet and speech reception thresholds in noise were also measured. A correlation coefficient of 0.85 between the speech discrimination score in quiet and the PSTI was obtained. For the speech reception threshold in noise and the PSTI, the correlation was 0.71. The first of these two figures is promising, but our method needs some improvement, as it gave some problems due to fatigue effects.     

Multi-channel compression and speech intelligibility in industrial noise.

This study examined how various forms of compression affect speech intelligibility in moderately high levels of industrial noise. Thirteen listeners with high-frequency sensorineural hearing loss were fit with a digital hearing aid programmed to operate in three modes of compression: compression limiting, compression of low frequencies only (BILL), and compression of high frequencies only (TILL). For each of these conditions, listeners attempted to recognize CID W-22 monosyllabic words delivered in a background of recorded industrial noise. Word recognition was also measured in quiet for the compression-limiting condition. The highest word identification scores were obtained in quiet (80.9%). Of the three conditions in which background noise was present, the mean score was highest for TILL compression (52.4%), and lowest for BILL (39.7%). Representative time-weighted average (TWA) exposures for each of the aided noise conditions were determined by means of a procedure outlined previously by the first author. The projected 8-hour amplified TWA with the hearing aid programmed to the TILL configuration was 94 dBA, whereas TWAs for the linear and BILL configurations were each 104 dBA. Thus, the highest intelligibility and lowest noise exposures were obtained with the aid in the TILL mode.     

The effect of stapedectomy on speech intelligibility in noise

Speech intelligibility in noise was tested pre- and postoperatively after 27 stapedectomy cases and 10 cases of reexploration after previous stapes surgery. We did not find a postoperative threshold shift (signal-to-noise ratio) for the intelligibility of sentences presented in noise. This finding corresponds well with the absence of postoperative high-frequency sensorineural loss in these patients. Using two types of prostheses we found a significant amelioration of speech intelligibility in quiet for the Schuknecht minihole prosthesis as compared to the House wire loop.     

Amplitude change with click rate in human brainstem auditory-evoked responses

The effect of click rate on wave amplitude of human brainstem auditory-evoked response (BAER) was examined at repetition rates of 10, 30, 50, 70 and 90 Hz in 80 healthy children aged 1 month to 6 years and in 21 adults. As repetition rate was increased from 10 to 90 Hz at 70 dB HL, the amplitudes in different age groups decreased by 33-45% (0.109-179 microV) for wave I and 25-41% (0.055-0.145 microV) for wave V. The older the children, the larger the absolute decrements of wave amplitudes with increasing repetition rate, but the relative decrements or reduction rates of wave amplitudes exhibited no systematically age-related differences. The V/I amplitude ratio tended to increase with increasing repetition rate in most age groups, suggesting that the amplitude of wave I is affected by the repetition rate slightly more than that of wave V. The patterns of the changes in wave amplitudes with repetition rate at lower intensity levels were essentially similar.     

Magnitude estimations of the intelligibility and quality of speech in noise

Inexperienced normal hearing listeners judged the intelligibility and quality of hearing aid processed speech using magnitude estimation. Four trials were conducted for each judgment type at two S/N ratios, 0 and 7 dB. There were no significant effects due to judgment type, S/N ratio or trial; however, noticeable differences in the variability of these factors were apparent. Inter- and intrasubject standard deviations for quality estimations were lower than for intelligibility estimations while intersubject standard deviations were greater at 0 dB than at 7 dB S/N ratio and decreased over trial. Overall intrasubject variability was greater than would probably be acceptable for clinical applications. Across hearing aid conditions, magnitude estimations were positively correlated with word recognition scores but were less affected by changes in S/N ratio.     

A simple audiometry test of speech intelligibility in background noise

We propose a new audiometric test to assess French speakers' speech discrimination in noise. This soundfield test uses a standard cocktail-party background noise superimposed on Fournier's disyllabic word lists. The background noise is CD-recorded at constant 55 dB SPL. The discrimination score is measured at a signal-to-noise ratio of -5 dB, 0, and dB. In comparison with other audiometric tests in noise, our test requires only 5 minutes and is simple for both patient and audiologist. All patients are tested using the same standard condition, one that approaches daily life and uses a noise of moderate intensity. The result is reproducible and easy to calculate and graph. We propose this test for diagnosing in-noise speech intelligibility disorders and for assisting the process of conventional or implantable hearing-aid fitting.     

Polish sentence matrix test for speech intelligibility measurement in noise

Abstract

The purpose of this study was to develop the Polish sentence matrix test (PSMT) to measure intelligibility of speech presented against a background noise. The PSMT consists of five columns containing: 10 names, 10 verbs, 10 numerals, 10 adjectives, and 10 nouns. Since each word was available as a separate sound file, it was possible to generate different sentences by juxtaposing randomly selected words taken from respective columns. This approach allows 100 000 unique sentences of a fixed grammatical structure to be generated. The speech reception threshold (SRT), i.e. the signal-to-noise ratio (SNR) providing 50% speech intelligibility and S₅₀, the slope of an intelligibility function at the SRT point, were shown to be ?9.6 dB and 17.1 %/dB, respectively. Note that in this study dB is regarded as dB SNR, otherwise reference is given. PSMT was also evaluated using an adaptive 1-up/ 1-down staircase procedure in investigations with and without participation of an experimenter. No significant differences were shown for SRTs obtained in these investigations.

Sumario

El propósito de este estudio fue desarrollar la prueba matriz de frases en polaco (PSMT) para medir la inteligibilidad de lenguaje presentado contra ruido de fondo. El PSMT consiste de cinco columnas que contienen: 10 nombres, 10 verbos, 10 numerales, 10 adjetivos y 10 palabras. Dado que cada palabra estaba disponible como un archivo de sonido separado, fue posible generar diferentes frases por medio de la yuxtaposición aleatoria de palabras seleccionadas tomadas de las respectivas columnas. Este enfoque permite la generación de 100.000 frases singulares con una estructura gramatical fija. El umbral de recepción del lenguaje (SRT), p.e., la tasa de señal-ruido (SNR) brindando el 50% de inteligibilidad del lenguaje, y el S50, la pendiente de una función de inteligibilidad en el punto del SRT, fueron –9.6 dB y 17.1%/dB, respectivamente. Note que en este estudio los dB corresponden a dB SNR, a menos que se brinde otra referencia. También se evaluó el PSMT usando un procedimiento adaptativo en escalera de 1 hacia arriba y 1 hacia abajo, en investigaciones con y sin un experimentador. No se encontraron diferencias significativas para los SRT obtenidos en estas investigaciones.     

Revision and validation of a binaural model for speech intelligibility in noise

Lavandier and Culling [Lavandier, M. and Culling, J. F. 2010. Prediction of binaural speech intelligibility against noise in rooms. J. Acoust. Soc. Am. 127, 387-399] demonstrated a method of predicting human speech reception thresholds for speech in combined noise and reverberation. An updated version of the model is presented, which is substantially more computationally efficient. The updated model makes similar predictions for the SRT data considered by Lavandier and Culling, which tested the model's ability to predict effects of binaural unmasking and room colouration. In addition, we show here that the model accurately predicts the effects of headshadow and reproduces a range of data sets from the literature, including situations with multiple interfering sounds in anechoic conditions.     

Improving speech intelligibility in background noise with an adaptive directional microphone

Omnidirectional, supercardioid, and adaptive directional microphones (ADM) were evaluated in combination with the ADRO amplification scheme for eight participants with moderate sloping hearing losses. The ADM produced better speech perception scores than the other two microphones in all noise conditions. Participants performed the Hearing in Noise Test sentences at -4.5 dB SNR or better, which is similar to the level achievable with normal hearing. The Speech, Spatial and Qualities of Hearing Scale indicated no disadvantages of using the ADM relative to the omnidirectional microphone in real-life situations. The ADM was preferred over the omnidirectional microphone in 54% of situations, compared to 17% preferences for the omnidirectional microphone, and 29% no preference. The combination of the ADM to improve SNR, and ADRO to keep the signal output comfortable and audible provided near-normal hearing performance for people with moderate hearing loss. The ADM is the recommended microphone configuration for ADRO hearing aids.     

Callsign Acquisition Test (CAT): speech intelligibility in noise

OBJECTIVE: The study was designed to assess the effects of noise on the intelligibility of speech elements used in the Callsign Acquisition Test (CAT), developed by the U.S. Army Research Laboratory. The CAT consists of 126 test items, or callsigns, each of which is made up of a two-syllable word selected from the 18-item military alphabet (Alpha-Zulu) followed by a one-syllable number (all numbers from 1 to 8, excluding 7). DESIGN: The CAT items were mixed with one of three different types of background noises (pink noise, white noise, and multitalker babble) and presented to 18 listeners. Speech-to-noise ratio for all three noises and the overall level of pink noise were varied in two separate experiments to determine how these variables affected speech intelligibility of the CAT items pronounced by a male talker. CONCLUSIONS: Test results demonstrate speech-to-noise ratio has a significant effect on speech intelligibility of the CAT items under all conditions. Pink noise generated the lowest speech intelligibility scores followed by multitalker babble and then white noise. A change in the overall level of pink noise had only small effect on CAT intelligibility.     

Relationship between speech motor control and speech intelligibility in children with speech sound disorders

The current study was undertaken to investigate the impact of speech motor issues on the speech intelligibility of children with moderate to severe speech sound disorders (SSD) within the context of the PROMPT intervention approach. The word-level Children's Speech Intelligibility Measure (CSIM), the sentence-level Beginner's Intelligibility Test (BIT) and tests of speech motor control and articulation proficiency were administered to 12 children (3:11 to 6:7 years) before and after PROMPT therapy. PROMPT treatment was provided for 45 min twice a week for 8 weeks. Twenty-four naïve adult listeners aged 22–46 years judged the intelligibility of the words and sentences. For CSIM, each time a recorded word was played to the listeners they were asked to look at a list of 12 words (multiple-choice format) and circle the word while for BIT sentences, the listeners were asked to write down everything they heard. Words correctly circled (CSIM) or transcribed (BIT) were averaged across three naïve judges to calculate percentage speech intelligibility. Speech intelligibility at both the word and sentence level was significantly correlated with speech motor control, but not articulatory proficiency. Further, the severity of speech motor planning and sequencing issues may potentially be a limiting factor in connected speech intelligibility and highlights the need to target these issues early and directly in treatment.     

Three-dimensional curves: main parameters of brainstem auditory-evoked responses in the normal subject

Brainstem evoked potentials (BER) have been studied in three dimensions (3D). It was necessary to record simultaneously three orthogonal derivations in the three spatial axes. The 3D curves obtained were formed by successive uncompletely locked loops which correspond with the first five waves of BER. Planar segment could be identified in the 3D curves; planes were defined by geometrical parameters, following standard analytic geometry. The 3D curves appeared to be symmetrical after right and left stimulation, and were almost completely flattened around the anteroposterior axis after binaural stimulation. This flattening was not observed in the case of multiple sclerosis.     

Effects of a transient noise reduction algorithm on speech intelligibility in noise,noise tolerance and perceived annoyance in cochlear implant users

Objective: To evaluate the validity and efficacy of a transient noise reduction algorithm (TNR) in cochlear implant processing and the interaction of TNR with a continuous noise reduction algorithm (CNR). Design: We studied the effects of TNR and CNR on the perception of realistic sound samples with transients, using subjective ratings of annoyance, a speech-in-noise test and a noise tolerance test. Study sample: Participants were 16 experienced cochlear implant recipients wearing an Advanced Bionics Naida Q70 processor. Results: CI users rated sounds with transients as moderately annoying. Annoyance was slightly, but significantly reduced by TNR. Transients caused a large decrease in speech intelligibility in noise and a moderate decrease in noise tolerance, measured on the Acceptable Noise Level test. The TNR had no significant effect on noise tolerance or on speech intelligibility in noise. The combined application of TNR and CNR did not result in interactions. Conclusions: The TNR algorithm was effective in reducing annoyance from transient sounds, but was not able to prevent a decreasing effect of transients on speech understanding in noise and noise tolerance. TNR did not reduce the beneficial effect of CNR on speech intelligibility in noise, but no cumulated improvement was found either.