Phonetics exercises using the Alvin experiment-control software.

Purpose: Exercises are described that were designed to provide practice in phonetic transcription for students taking an introductory phonetics course. The goal was to allow instructors to offload much of the drill that would otherwise need to be covered in class or handled with paper-and-pencil tasks using text rather than speech as input.

Method: The exercises were developed using Alvin, a general-purpose software package for experiment design and control.

Perception of sinewave vowels.

There is a significant body of research examining the intelligibility of sinusoidal replicas of natural speech. Discussion has followed about what the sinewave speech phenomenon might imply about the mechanisms underlying phonetic recognition. However, most of this work has been conducted using sentence material, making it unclear what the contributions are of listeners' use of linguistic constraints versus lower level phonetic mechanisms.

The role of f (0) and formant frequencies in distinguishing the voices of men and women.

The purpose of the present study was to determine the contributions of fundamental frequency (f (0)) and formants in cuing the distinction between men's and women's voices. A source-filter synthesizer was used to create four versions of 25 sentences spoken by men: (1) unmodified synthesis, (2) f (0) only shifted up toward values typical of women, (3) formants only shifted up toward values typical of women, and (4) both f (0) and formants shifted up. Identical methods were used to generate four corresponding versions of 25 sentences spoken by women, but with downward shifts.

Speech perception based on spectral peaks versus spectral shape.

This study was designed to measure the relative contributions to speech intelligibility of spectral envelope peaks (including, but not limited to formants) versus the detailed shape of the spectral envelope. The problem was addressed by asking listeners to identify sentences and nonsense syllables that were generated by two structurally identical source-filter synthesizers, one of which constructs the filter function based on the detailed spectral envelope shape while the other constructs the filter function using a purposely coarse estimate that is based entirely on the distribution of peaks in the envelope. Viewed in the broadest terms the results showed that nearly as much speech information is conveyed by the peaks-only method as by the detail-preserving method.

Open source software for experiment design and control.

The purpose of this paper is to describe a software package that can be used for performing such routine tasks as controlling listening experiments (e.g., simple labeling, discrimination, sentence intelligibility, and magnitude estimation), recording responses and response latencies, analyzing and plotting the results of those experiments, displaying instructions, and making scripted audio-recordings.

A narrow band pattern-matching model of vowel perception.

The purpose of this paper is to propose and evaluate a new model of vowel perception which assumes that vowel identity is recognized by a template-matching process involving the comparison of narrow band input spectra with a set of smoothed spectral-shape templates that are learned through ordinary exposure to speech. In the present simulation of this process, the input spectra are computed over a sufficiently long window to resolve individual harmonics of voiced speech. Prior to template creation and pattern matching, the narrow band spectra are amplitude equalized by a spectrum-level normalization process, and the information-bearing spectral peaks are enhanced by a "flooring" procedure that zeroes out spectral values below a threshold function consisting of a center-weighted running average of spectral amplitudes.

Speech synthesis using damped sinusoids.

A speech synthesizer was developed that operates by summing exponentially damped sinusoids at frequencies and amplitudes corresponding to peaks derived from the spectrum envelope of the speech signal. The spectrum analysis begins with the calculation of a smoothed Fourier spectrum. A masking threshold is then computed for each frame as the running average of spectral amplitudes over an 800-Hz window.