Friday, September 30, 1:30 pm — 3:00 pm (Rm 403A)
Bob Schulein, ImmersAV Technology - Schaumburg, IL, USA
P12-1 Development of Shotgun Microphone with Extra-Long Leaky Acoustic Tube—Yo Sasaki, NHK Science & Technology Research Laboratories - Kinuta, Setagaya-ku, Tokyo, Japan; Toshiyuki Nishiguchi, NHK Science & Technology Research Laboratories - Setagaya, Tokyo, Japan; Kazuho Ono, NHK Science & Technology Research Laboratories - Setagaya-ku, Tokyo, Japan; Takeshi Ishii, Sanken Microphone Co. Ltd. - Tokyo, Japan; Yutaka Chiba, Sanken Microphone Co. Ltd. - Tokyo, Japan; Akira Morita, Sanken Microphone Co. Ltd. - Tokyo, Japan
A shotgun microphone having sharper directivity than a conventional microphone has been studied to capture distant sound clearly. The directivity of the shotgun microphone is known to become sharper with a longer leaky acoustic tube. Thus, we developed a prototype microphone that uses a 1-m-long leaky acoustic tube, which is longer than the conventional one. We also conducted a numerical simulation based on an acoustical distribution constant circuit to develop such a shotgun microphone. The measurement results of the prototype microphone were in fairly good agreement with the simulation results, and they showed that the directivity is very narrow.
Convention Paper 9639 (Purchase now)
P12-2 Non-Traditional Noise and Distortion Sources in Headphones and Earbuds and Their Impact on System Performance and Ear Fatigue—Dennis Rauschmayer, REVx Technologies/REV33 - Austin, TX, USA
Non-Traditional dynamic noises and distortions that couple into earbuds and headphones are measured and analyzed. The effective noise and distortion level relative to the signal level for a number of commercially available headphones and earbuds are reported. The impact of this noise and distortion on listener experience is quantified and discussed. Finally, the impact on listener fatigue is quantified. Results presented show that the non-traditional sources studied are significant, audible and that they present a fundamental limitation to the performance of many earbuds and headphones. In many cases, these sources reduce the effective signal to noise ratio (SNR) of the audio system into the 30-40 dB range, well below the SNR level that would result from by a 0.1% total harmonic distortion (THD) system and even below that of a 1% THD system. In addition to limiting system performance, the non-traditional noise and distortion are found to increase ear fatigue experienced by the user when ear fatigue tests are conducted with identical audio levels. Otoacoustic Emission (OAE) results from tested subjects show degradation that is significantly greater when the impairments are present vs. when they are mitigated.
Convention Paper 9640 (Purchase now)
P12-3 In Situ Subjective and Objective Acoustic Seal Performance Tests for Insert Earphones—Bob Schulein, ImmersAV Technology - Schaumburg, IL, USA; Brian Fligor, Lantos Technologies Inc. - Wakefield, MA, USA
Insert–type earphones are unique in that when tightly sealed in an ear canal, they have the potential to deliver sound down to 20 Hz and below. In practice however, obtaining an extended low frequency response is challenged by a difficulty for users to achieve an adequate seal between the ear canal and the insert earphone , , . Achieving such a seal is not intuitive to users new to insert earphones. Measurements made on actual earphones show that a leak as small as .5 mm in diameter and 2.5 mm long can result in a reduction of bass at 50 Hz of approximately 15 dB. Such a loss results when the leak is present, since the actual volume seen by the transducer at low frequencies is considerably greater than for higher frequencies, where the impedance of the leak becomes much higher in value. The result is a very perceptible and often disappointing reduction in bass performance. This paper describes two methods by which a user can confirm the level of acoustic seal obtained for a given combination of transducer, ear tip / ear mold and ear canal by subjective and objective means. The subjective method is based on an experimental observation that even with a poor seal the output of insert earphones at 500 Hz, is quite independent of seal quality. By consequently subjectively comparing the output of a recorded tone at 500 Hz to one at 50 Hz adjusted to be equal in perceived level based on ISO 226:2003 equal-loudness contours, one can confirm a good seal when the levels tend to subjectively match. The objective method involves fitting an insert earphone with a miniature flat pressure microphone into the sound port, and observing the “in canal” frequency response by means of spectral analysis, while the earphone is in use. As the seal quality improves the measured low frequency response approaches that of the coupler response of the earphone as measured with a high quality seal.
Convention Paper 9641 (Purchase now)