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Last Updated: 20070405, mei

P21 - Instrumentation and Measurement

Tuesday, May 8, 09:00 — 12:30

Chair: Heinrich Pichler, Technical University of Vienna - Vienna, Austria

P21-1 Advancements in Impulse Response Measurements by Sine SweepsAngelo Farina, University of Parma - Parma, Italy
Sine sweeps have been employed for long time for audio and acoustics measurements, but in recent years (2000 and later) their usage became much larger, thanks to the computational capabilities of modern computers. Recent research results now allow for a further step in sine sweep measurements, particularly when dealing with the problem of measuring impulse responses, distortion, and when working with systems that are neither time invariant nor linear. The paper present some of these advancements and provide experimental results aimed to quantify the improvement in signal-to-noise ratio, the suppression of pre-ringing, and the techniques employed for performing these measurements cheaply using a standard PC and a good-quality sound interface, and currently available loudspeakers and microphones.
Convention Paper 7121 (Purchase now)

P21-2 The Challenges of MP3 Player TestingSteve Temme, Pascal Brunet, Zachary Rimkunas, Listen, Inc. - Boston, MA, USA
MP3 player audio performance is discussed including measurements of frequency response, phase response, crosstalk, distortion, sampling rate errors, jitter, and maximum sound pressure level with headphones. In order to make these measurements, several measurement techniques and algorithms are presented to overcome some of the challenges of testing MP3 players. We discuss test equipment requirements, selection of test signals, and the effects of the encoding on these test signals. A new method for measuring noncoherent distortion using any test signal including music is also presented.
Convention Paper 7122 (Purchase now)

P21-3 Tracking Harmonics and Artifacts in Spectra Using Sinusoidal and Spiral MapsPalmyra Catravas, Union College - Schenectady, NY, USA
A technique for tracking a harmonic series in a spectrum using a combination of sinusoidal and spiral maps is described. The spiral map enhances patterns that appear when a sinusoid is sampled near the Nyquist rate. The correspondence between the maps facilitates derivation of properties and motivates the use of curves that cut across the sinusoid or spiral. As an application, the spatial separation of a specific musical pitch from an artifact is demonstrated.
Convention Paper 7123 (Purchase now)

P21-4 Spatial Distribution Meter: A New Method to Display Spatial Impression Over TimeJoerg Bitzer, University of Applied Science Oldenburg - Oldenburg, Germany
A wide-spread method for visualizing the spatial behavior of stereo signals is the vector-scope or goniometer, which shows the relation between the left and right channel. Well-trained eyes can see misbalance and mono compatibility problems in these very fast changing figures. However, this analysis tool contains no information over time and no details can be seen. In this paper we introduce a new method for analyzing stereo signals, which is based on the vector-scope but shows the behavior over time. The final graph looks like a spectrogram/sonogram, where the axes are time and angle. Useful applications of this new spatial distribution meter are the analysis of stereo impulse responses, the shift of stereo base over time, and the typical applications of a vector-scope.
Convention Paper 7124 (Purchase now)

P21-5 Low Level Audio Signal Transfer Through Transformer Conflicts with Permeability Behavior Inside Their CoresMenno van der Veen, ir. bureau Vanderveen bv - Zwolle, The Netherlands
At the threshold of audibility, the signal and flux density levels in an amplifier with audio transformers are very small. At those levels the relative magnetic permeability of the iron transformer core collapses and the inductance of the transformer becomes very small. The impedances connected to the transformer plus its signal level and frequency-dependant inductance behave as a high pass filter that corner frequencies slip into the audio bandwidth, resulting in a nonlinear signal transfer through the transformer. This paper explains deviations in the reproduction of micro details at the threshold of audibility.
Convention Paper 7125 (Purchase now)

P21-6 New Techniques for Measuring Speech Privacy and Efficiency of Sound Masking SystemsPeter Mapp, Peter Mapp Associates - Colchester, Essex, UK
Speech privacy is becoming an increasingly important aspect for many workplace and security environments as well as hospital and medical centers where patient confidentially is of critical importance. Traditionally, speech privacy has been measured by means of the Articulation Index, transposed to rate privacy rather than intelligibility (PI=1-AI). However, this is an indirect and cumbersome method that usually requires a spreadsheet calculation to yield the Privacy Index rating. The paper discusses the potential use of STI and STIPa as direct measures of speech privacy. The benefits and limitations of the methods are highlighted together with the results from a number of case studies. It is concluded that while the method has potential merit, a number of the limiting factors require further research.
Convention Paper 7126 (Purchase now)

P21-7 Onset Detection Method in Piano Music: Sensibility to Threshold ValuesLuis Ortiz-Berenguer, Javier Casajus-Quiros, Marison Torres-Guijarro, Jon Beraceochea, Technical University of Madrid - Madrid, Spain
Piano music transcription requires a stage of onset detection. Every time a new note or chord is played, a new analysis of the note or chord is needed. It is a critical issue to correctly detect if a new note or chord has been played. Onset detection should have a simple solution, but several problems arise when attempting to perform it. This paper present a study of the sensibility of a detection method depending on the adjustable parameters. It also compares some results with a simpler method based on the analysis of the derivative of the energy envelope. The methods have been tested with six piano compositions. As a conclusion, accurate automatic onset detection in piano music is not a simple task even in the case of notes played alone.
Convention Paper 7127 (Purchase now)