Narrow-band Envelopes Research Articles

The effect of permutations of time samples in the speech waveform on intelligibility.

This paper describes the effect of two types of temporal permutations of the speech waveform on speech intelligibility. Using an overlap-add procedure with triangular-shaped windows for frame lengths of 1/8 to 2048 ms, the temporal order of the speech samples within each frame was subjected to either of two types of permutations: time-reversal or randomization. For both permutations, speech intelligibility tests expectantly show 100% intelligibility for the very short frame lengths containing only a few speech samples. Intelligibility drops to essentially zero toward longer frame lengths of around 1 ms. Interestingly, only for the reverse condition, intelligibility recovers to essentially 100% for frame lengths in the 4-32 ms range, dropping again to zero for frame lengths exceeding about 100 ms. Tests for the Japanese and the English language show essentially similar results. The data are interpreted along the lines of a previous paper by Kazama and the present authors [J. Acoust. Soc. Am. 127(3), 1432-1439 (2010)]. As in that previous paper, the loss of temporal envelope correlation shows a pattern very similar to that of the intelligibility data, illustrating again the importance of the preservation of narrow-band envelopes for speech intelligibility.

Effects of temporal and spectral factors of maskers on speech intelligibility

This study demonstrates a new possibility of estimating intelligibility of speech in informational maskers. The temporal and spectral properties of sound maskers are investigated to achieve acoustic privacy in public spaces. Speech intelligibility (SI) tests were conducted using Japanese sentences in daily use for energy (white noise) or informational (reversed speech) maskers. We found that the masking effects including informational masking on SI might not be estimated by analyzing the narrow-band temporal envelopes, which is a common way of predicting SI under noisy conditions. The masking effects might instead be visualized by spectral auto-correlation analysis on a frame-by-frame basis, for the series of dominant-spectral peaks of the masked target in the frequency domain. Consequently, we found that dissimilarity in frame-based spectral-auto-correlation sequences between the original and masked targets was the key to evaluating maskers including informational masking effects on SI.

On the significance of phase in the short term Fourier spectrum for speech intelligibility

This paper investigates the significance of the magnitude or the phase in the short term Fourier spectrum for speech intelligibility as a function of the time-window length. For a wide range of window lengths (1/16-2048 ms), two hybrid signals were obtained by a cross-wise combination of the magnitude and phase spectra of speech and white noise. Speech intelligibility data showed the significance of the phase spectrum for longer windows (>256 ms) and for very short windows (<4 ms), and that of the magnitude spectrum for medium-range window lengths. The hybrid signals used in the intelligibility test were analyzed in terms of the preservation of the original narrow-band speech envelopes. Correlations between the narrow-band envelopes of the original speech and the hybrid signals show a similar pattern as a function of window length. This result illustrates the importance of the preservation of narrow-band envelopes for speech intelligibility. The observed significance of the phase spectrum in recovering the narrow-band envelopes for the long term windows and for the very short term windows is discussed.

Contribution of Spectrotemporal Features on Auditory Event-Related Potentials Elicited by Consonant-Vowel Syllables

To determine the influence of spectrotemporal properties of naturally produced consonant-vowel syllables to speech-evoked auditory event-related potentials (ERPs) for stimuli with very similar or even identical wide-band envelopes. Speech-evoked ERPs may be useful for validating the neural representation of speech. Speech-evoked ERPs were obtained from 10 normal-hearing young adults in response to the syllables /da/ and /ta/. Both monosyllables were obtained from ongoing speech. They have quite similar wide-band envelopes, and they mainly differ in the spectrotemporal content of the consonant parts. Additionally, each stimulus derivatives were investigated with (1) isolated consonant part ("consonant stimulus"), (2) isolated vowel part ("vowel stimulus"), and (3) removed spectral information but identical wide-band envelope. Latencies and amplitudes of the N1 and P2 components were determined and analyzed. ERPs in response to the naturally produced /ta/ syllable had significant shorter N1 and P2 latencies and larger amplitudes than ERPs in response to /da/. Similar differences were observed for the ERPs evoked by the consonant stimuli alone. For the vowel stimuli and stimuli with removed spectral information, no significant differences were observed. In summary, differences between the ERPs of /da/ and /ta/ corresponded to the distinct spectrotemporal content in the consonant parts of the original consonant-vowel (CV) syllables. The study shows that even small differences in spectrotemporal features of speech may evoke different ERPs, despite very similar or even identical wide-band envelopes. The results are consistent with a model that ERPs evoked by short CVs are an onset response to the consonant merged with an acoustic change complex evoked by the vowel part. However, all components appear as one P1-N1-P2 complex. The results may be explained by differences in the narrow-band envelopes of the stimuli. Therefore, this study underlines the limitations of the wide-band envelope in explaining speech-evoked ERPs. Additionally, the results of this study are of special interest for clinical application since some of the ERP parameter differences, as the N1 latency, are present not only in the ERPs of each single subject but also in the group mean value of all N1 latencies. Thus, presented ERP measurements in response to CVs might be used for identification of potential problems in phoneme differentiation caused by spectrotemporal analysis problems.

Brief Communication: The Prevalence of High Intake of Vitamin E From the Use of Supplements Among U.S. Adults

Intelligibility is the key factor in speech communication. Reverberation or surrounding noise is an adverse condition to the intelligibility from an acoustical perspective. Reverberation effects on the intelligibility can be characterized by the ratio of the direct energy to its reverberant energy, which depends on the distance from the source (or talker). The direct sound, from a perceptual perspective, may be extended into a superposition of the direct and following early echoes within around 30(ms) after the direct echo. These early echoes may help increase the direct sound, even under reverberant conditions, rather than decrease intelligibility due to reflected sounds. On the other hand, the intelligibility is conveyed in the narrowband envelopes (around 1/4−octave band). Assuming a reverberant space to be a linear system of sound wave transmission, the modulation index (or spectral magnitude) of a modulated sound decreases due to transmission through reverberant space. The decrease in the modulation index decreases the intelligibility as the sound source distance increases. Effects of sound absorption or arrays of sound sources on the intelligibility are illustrated by increasing the energy ratio. The arrangement of sound absorbers that creates steep initial slopes of the reverberation decay curves implies the possibility of designing an auditorium that combines intelligible speech with rich reverberation of music.

Management and Outcomes of Elderly Women and Men With Acute Coronary Syndromes in 2000 and 2002

Signal dynamics is representative of perceptual signatures of sound in the time domain. Narrowband envelopes expressing frequency-dependent signal dynamics are keys to estimating intelligibility of speech materials. On the other hand, waveforms can be decomposed into the magnitude and phase spectral components in the frequency domain. An interesting question from a perceptual frame of reference would be whether the magnitude- or phase-spectral component is dominant for speech samples to be intelligible. This chapter investigates the spectral dominance on the intelligibility through synthesizing spectrally (magnitude or phase) or temporally modified (reversed or random permutation) speech materials and listening tests. Results confirm that keeping narrowband envelopes is significant in order to preserve the intelligibility of speech materials. For the preservation of narrowband envelopes or the frequency-dependent signal dynamics in the time domain, the spectral dominance may be temporally dependent. Frame-wise (temporally dependent) spectral analysis reveals the magnitude-spectral dominance in the medium range of frame lengths around 30(ms) for speech to be intelligible, while the phase may be significant in other shorter or longer frame length conditions. The magnitude dominance region provides appropriate frame length conditions for frequency resolution for selecting narrowband frequencies such as 1/4-octave band and temporal resolution for envelope periods. In contrast, the spectral structure obtained in the longer frame length conditions is fine enough to reconstruct the envelopes from the phase. In the very shorter frame length conditions, the micro structure of the waveform such as zero-crossings in the time domain could be preserved so that the envelopes are preserved by the phase spectrum.

Clinical Outcomes in Antihypertensive Treatment of Type 2 Diabetes, Impaired Fasting Glucose Concentration, and Normoglycemia: Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT)

Intelligibility is the key factor in speech communication. Reverberation or surrounding noise is an adverse condition to the intelligibility from an acoustical perspective. Reverberation effects on the intelligibility can be characterized by the ratio of the direct energy to its reverberant energy, which depends on the distance from the source (or talker). The direct sound, from a perceptual perspective, may be extended into a superposition of the direct and following early echoes within around 30(ms) after the direct echo. These early echoes may help increase the direct sound, even under reverberant conditions, rather than decrease intelligibility due to reflected sounds. On the other hand, the intelligibility is conveyed in the narrowband envelopes (around 1/4−octave band). Assuming a reverberant space to be a linear system of sound wave transmission, the modulation index (or spectral magnitude) of a modulated sound decreases due to transmission through reverberant space. The decrease in the modulation index decreases the intelligibility as the sound source distance increases. Effects of sound absorption or arrays of sound sources on the intelligibility are illustrated by increasing the energy ratio. The arrangement of sound absorbers that creates steep initial slopes of the reverberation decay curves implies the possibility of designing an auditorium that combines intelligible speech with rich reverberation of music.

A Randomized Trial Comparing 2 Low-Molecular-Weight Heparins for the Outpatient Treatment of Deep Vein Thrombosis and Pulmonary Embolism

Intelligibility is the key factor in speech communication. Reverberation or surrounding noise is an adverse condition to the intelligibility from an acoustical perspective. Reverberation effects on the intelligibility can be characterized by the ratio of the direct energy to its reverberant energy, which depends on the distance from the source (or talker). The direct sound, from a perceptual perspective, may be extended into a superposition of the direct and following early echoes within around 30(ms) after the direct echo. These early echoes may help increase the direct sound, even under reverberant conditions, rather than decrease intelligibility due to reflected sounds. On the other hand, the intelligibility is conveyed in the narrowband envelopes (around 1/4−octave band). Assuming a reverberant space to be a linear system of sound wave transmission, the modulation index (or spectral magnitude) of a modulated sound decreases due to transmission through reverberant space. The decrease in the modulation index decreases the intelligibility as the sound source distance increases. Effects of sound absorption or arrays of sound sources on the intelligibility are illustrated by increasing the energy ratio. The arrangement of sound absorbers that creates steep initial slopes of the reverberation decay curves implies the possibility of designing an auditorium that combines intelligible speech with rich reverberation of music.

Elevated Levels of High-Sensitivity C-Reactive Protein and Serum Amyloid-A Late After Kawasaki Disease: Association Between Inflammation and Late Coronary Sequelae in Kawasaki Disease

Narrowband envelopes of audible sounds are keys to the perception of signals conveyed by those sounds, known as speech intelligibility. The decomposition of waveforms into envelopes and their carriers is based on the analytic representation of waveforms. This chapter summarizes a theoretical approach to getting analytic representation as a complex function from a waveform in a real function. The complex function with the instantaneous magnitude (or envelope) and the instantaneous phase in the time domain could be interpreted as the relationship between the magnitude and phase spectra in the frequency plane. Masking effects are representative losses of speech intelligibility under noisy environments. Informational masking effects are displayed on the spectral fine-structure, too, that might be hidden in the carrier rather than the envelope of intelligible speech, as well as energy masking effects on the envelopes by a white noise masker. Interestingly, time-reversed speech masker would be a representative for the informational carrier, while a white noise is a typical example of energy maskers.