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AES Munich 2009
Paper Session P22

P22 - Microphones and Headphones

Saturday, May 9, 15:00 — 18:30
Chair: William Evans, University of Surrey - Guildford, Surrey, UK

P22-1 Frequency Response Adaptation in Binaural HearingDavid Griesinger, Consultant - Cambridge, MA, USA
The pinna and ear canals act as listening trumpets to concentrate sound pressure on the eardrum. This concentration is strongly frequency dependent, typically showing a rise in pressure of 20 dB at 3000 Hz. In addition, diffraction and reflections from the pinna substantially alter the frequency response of the eardrum pressure as a function of the direction of a sound source. In spite of these large departures from flat response, listeners usually report that a uniform pink power spectrum sounds frequency balanced, and loudspeakers are manufactured to this standard. But on close listening frontal pink noise does not sound uniform. The ear clearly uses adaptive correction of timbre to achieve these results. This paper discusses and demonstrates the properties and limits of this adaptation. The results are important for our experience of live music in halls and in reproduction of music through loudspeakers and headphones.
Convention Paper 7768 (Purchase now)

P22-2 Concha Headphones and Their Coupling to the EarLola Blanchard, Bang & Olufsen ICEpower s/a - Lyngby, Denmark; Finn T. Agerkvist, Technical University of Denmark - Lyngby, Denmark
The purpose of the study is to obtain a better understanding of concha headphones. Concha headphones are the small types of earpiece that are placed in the concha. They are not sealed to the ear and therefore, there is a leak between the earpiece and the ear. This leak is the reason why there is a significant lack of bass when using such headphones. This paper investigates the coupling between the headphone and the ear, by means of measurement in artificial ears and models. The influence of the back volume is taken into account.
Convention Paper 7769 (Purchase now)

P22-3 Subjective Evaluation of Headphone Target Frequency ResponsesGaëtan Lorho, Nokia Corporation - Finland
The effect of headphone frequency response equalization on listeners’ preference was studied for music and speech reproduction. The high-quality circum-aural headphones selected for this listening experiment were first equalized to produce a flat frequency response. Then, a set of filters was created based on two parameters defining the amplitude and center frequency of the main peak found around 3 kHz in the free-field and diffuse-field equalization curves. Two different listening tests were carried out to evaluate these equalization candidates using a different methodology and a total of 80 listeners. The results of this study indicate that a target frequency response with a 3 kHz peak of lower amplitude than in the diffuse-field response is preferred by listeners for both music and speech.
Convention Paper 7770 (Purchase now)

P22-4 Study and Consideration on Symmetrical KEMAR HATS Conforming to IEC60959Kiyofumi Inanaga, Homare Kon, Sony Corporation - Tokyo, Japan; Gunnar Rasmussen, Per Rasmussen, G.R.A.S. Sound & Vibration A/S - Holte, Denmark; Yasuhiro Riko, Riko Associates - Yokohama, Japan
KEMAR is widely recognized as a leading model of head and torso simulators (HATS) for different types of acoustic measurements meeting requirements of a global industrial standard, ANSI S3.36/ASA58-1985 and IEC 60959:1990. One of the KEMAR HATS pinna models has a reputation for good reproducibility of measured results in examining headphones and earphones. However, it requires free filed compensation in order to conduct the measurements; thus, the head-related transfer function (HRTF) of HATS fitted with the pinna model must be corrected. Because headphones and earphones are usually designed symmetrically, we developed a prototype of Symmetrical KEMAR HATS based on the original KEMAR mounted with the pinna model with good reproducibility. We measured and evaluated a set of HRTFs from the sound source to both ears. Our study concluded that the HATS we developed carries symmetrical characteristics and is also suitable to be utilized as a tool to measure the qualities of variety of acoustic devices along with the conventional KEMAR and it can serve as a new common platform for different types of electroacoustic measurements.
Convention Paper 7771 (Purchase now)

P22-5 Spatio-Temporal Gradient Analysis of Differential Microphone ArraysMihailo Kolundzija, Christof Faller, Ecole Polytechnique Fédérale de Lausanne - Lausanne, Switzerland; Martin Vetterli, Ecole Polytechnique Fédérale de Lausanne - Lausanne, Switzerland, University of California at Berkeley, Berkeley, CA, USA
The literature on gradient and differential microphone arrays makes a distinction between the two, and nevertheless shows how both types can be used to obtain the same response. A more theoretically sound rationale for using delays in differential microphone arrays has not yet been given. This paper presents a gradient analysis of the sound field viewed as a spatio-temporal phenomenon, and gives a theoretical interpretation of the working principles of gradient and differential microphone arrays. It shows that both types of microphone arrays can be viewed as devices for approximately measuring the spatio-temporal derivatives of the sound field. Furthermore, it also motivates the design of high-order differential microphone arrays using the aforementioned spatio-temporal gradient analysis.
Convention Paper 7772 (Purchase now)

P22-6 The Analog Microphone Interface and its HistoryJoerg Wuttke, Joerg Wuttke Consultancy - Pfinztal, Germany, Schoeps GmbH, Karlsruhe, Germany
The interface between microphones and microphone inputs has special characteristics and requires special attention. The low output levels of microphones and the possible need for long cables have made it necessary to think about noise and interference of all kinds. A microphone input is also the electrical load for a microphone and can have an adverse influence on the its performance. Condenser microphones contain active circuitry that required some form of powering. With the introduction of transistorized circuitry in the 1960s, it became practical for this powering to be incorporated into microphone inputs. Various methods appeared in the beginning; 48-Volt phantom powering is now the dominant standard, but this standard method is still not always implemented correctly.
Convention Paper 7773 (Purchase now)

P22-7 Handling Noise Analysis in Large Cavity Microphone Windshields—Improved SolutionPhilippe Chenevez, CINELA - Paris, France
Pressure gradient microphones are well known to be highly sensitive to vibrations. Respectable suspensions are made to create the best isolation possible, but when the microphone is placed inside a large cavity windshield, the external skin behaves as a drum excited by the vibrations of the support (boom or stand). As a consequence structure-borne noise is also transmitted acoustically to the microphone, due to its hard proximity effect. Some theoretical aspects and practical measurements are presented, in conjunction with a proposed improved solution.
Convention Paper 7774 (Purchase now)