2:00 pm

I-1 Bayesian Harmonic Analysis for Audio Testing and Measurement

Thomas J. Loredo, Muse, Ithaca, NY, USA

Many common audio test and measurement procedures require characterization of the output signal of the device under test in terms of harmonic (sinusoidal) components and residual noise when the device processes sinusoidal input signals. This work uses the Bayesian approach to statistical inference to address such problems as parameter estimation problems when discrete samples of the output signal are given. In the resulting Bayesian harmonic analysis the power spectrum computed from the discrete-time Fourier transform appears as the logarithm of the posterior probability for the frequency of a single sinusoid rather than as an estimate of the signal spectrum; more complicated functions of the transform arise when analyzing signals with multiple sinusoids. Problems such as spectral leakage are addressed by nonlinear processing of the Fourier transform, offering several advantages over methods that use (linear) windowing of data.

Convention Paper 5447

2:30 pm

I-2 Measurement, Analysis, and Visualization of Directional Room Responses

Juha Merimaa, Tapio Lokki and Matti Karjalainen, Helsinki University of Technology, Espoo, Finland
Timo Peltonen, Akukon OY Consulting Engineers, Helsinki, Finland

Room impulse responses are inherently multidimensional, including components in three coordinate directions, each one further being described as a time-frequency representation. Such 5-dimensional data is difficult to visualize and interpret. We propose methods that apply 3-D microphone arrays, directional analysis of measured room responses, and visualization of data, yielding useful information about the time-frequency-direction properties of the responses. The applicability of the methods is demonstrated with three different cases of real measurements.

Convention Paper 5449

3:00 pm

I-3 New Factors in Room Equalization Using a Fuzzy Logic Approach

Sunil Bharitkar and Chris Kyriakakis, University of Southern California, Los Angeles, CA, USA

Room acoustical modes, particularly in small rooms, cause a significant variation in the room responses measured at different locations. Responses measured only a few cm apart can vary by up to 15-20 dB at certain frequencies. This makes it difficult to equalize an audio system for multiple simultaneous listeners. Previous methods have utilized multiple microphones and spatial averaging with equal weighting. In this paper we present a different multiple point equalization method. We first determine representative prototypical room responses derived from several room responses that share similar characteristics, using the fuzzy unsupervised learning method. These prototypical responses can then be combined to form a general point response. When we use the inverse of the general point response as an equalizing filter, our results show a significant improvement in equalization performance over the spatial averaging methods. Applications of this method include equalization and multiple point sound control at home and in automobiles.

Convention Paper 5450

3:30 pm

I-4 Development of Test Signals for the EIA-426-B Loudspeaker Power - Rating Compact Disk

D. B. (Don) Keele Jr., Harman/Becker Automotive Systems, Martinsville, IN, USA

The EIA-426-B standard: "Loudspeakers, Optimum Amplifier Power" (April 1998) specifies a test CD that contains the calibration and test signals for all the tests defined in the standard. This CD is intended to improve the consistency and convenience of the standard and will be made available through the EIA and other sources. This paper describes the development process of the signals placed on the CD with emphasis on the spectral-shaped random noise signal used for life testing and the variable-rate sine-wave sweep test signal used for power compression tests. All signals were generated analytically using a signal processing and data analysis program. In the process of creating the signals, a couple of errors were detected in the standard in its description of the method for generating the variable-rate sweep signal. The paper also develops the math for generating variable-rate sweeps whose spectrums roll-off at an arbitrary given rate. Complete statistics and measurements are described for the signals as placed on the CD and for the signals as played back on a typical CD player. Also described are a series of 6.5-cycle shaped tone bursts that are included on the CD. These are intended for use as a test stimulus for short-term power assessment of loudspeakers and electronics, and for testing the frequency response, energy decay and narrow-band phase/polarity of systems.

Convention Paper 54451

4:00 pm

I-5 Spectral Approach to the Modeling of the Singing Voice

Jordi Bonada, Alex Loscos, Pedro Cano and Xavier Serra, Pompeu Fabra University, Barcelona, Spain
Hideki Kenmochi, Yamaha Corporation, Hamamatsu, Japan

In the last three years we have been working in the development of two different applications related to the singing voice synthesis: an automatic voice impersonator for karaoke systems and a singing synthesizer. In this paper we will present each of these applications along with each of their specific approach to the singing voice modeling problem.

Convention Paper 5452

4:30 pm

I-6 Characterizing Digital Audio Transformers with Induced Jitter Histograms

Jon D. Paul, Scientific Conversion, Inc., Novato, CA, USA

Transformers are employed in digital audio systems primarily to reject common mode noise interference, to break ground loops and to enhance balance to avoid inductive emissions. A new test characterizes the interference rejection of a practical transmission system with a transformer at the receiver input. A sample set of decoded frame sync clocks are accumulated by a statistical time interval analyzer. The analyzer calculates the mean value of the periods, the standard deviation (jitter), and provides a period histogram. The histogram and standard deviation establish a basis for comparing the high frequency interference rejection of various transformers and for quantifying the nature of the induced jitter. Test data are presented for 7 different types of transformers.

Convention Paper 5448