Two Methods to Test Transducer Array Directivity

Abstract:

An array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. In order to test transducer directivity, two methods are designed. The one is to measure the ultrasonic sound pressure level by instruments. The sound pressure level is measured at multiple points to deduce the directivity angle of the acoustic transducer array. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°; higher frequencies will lead to the side lobes, but it can be negligible when compared to the main lobe. The other method is using the frequency analyzer to test transducer directivity in a silencer chamber. The sound pressure level can be read out from frequency response diagrams. The angle between the sound pressure value that decreasing 3db from the max value 111.7db and the max value is about 11°. So the directivity acute angle is about 11°. It should be noticed that, as the directivity diagram can not be directly attributed, there is some deviation in the conclusion.

• Periodical: Advanced Materials Research (Volumes 912-914)
• Pages: 1485-1488
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.912-914.1485
• Online since: April 2014
• Authors: Hong Liu*, Guo Zhu Zhao
• Keywords: Amplifier, Directional Audio, Directivity Pattern, Impedance Analysis, Transducer

References

[1] Chen Min. Research on the Fundamental Theory and Key Technologies of Audio Directional System [PhD]. University of Electronic Science and Technology of China, (2008).

[2] Masashi Yamada, Nobuyuki Itsuki, Yohsuke Kinouchi. Adaptive Directivity Control of Speaker Array[J]. Proceedings of the 8th International Conference on Control, Automation, Robotics and Vision, Kunming, China, Dec 6-9, (2004).

DOI: 10.1109/icarcv.2004.1469061

[3] M. Yoneyama, J. -I. Fujimoto. The Audio Spotlight: An Application of Nonlinear Interaction of Sound Waves to a New Type of Loudspeaker Design[J]. The Journal of the Acoustical Society of America, (1983).

DOI: 10.1121/1.389414

[4] Woon-Seng Gan, Jun Yang, Khim-Sia Tan, et al. A Digital Beamsteerer for Difference Frequency in a Parametric Array[J]. IEEE Transactions on Audio, Speech and Language Processing(2006).

DOI: 10.1109/tsa.2005.857786

[5] T. Kamakura, T. Yoneyama and K. Ikegaya. Studies for the Realization of Parametric Loudspeaker[J]. Journal of Acoustic Society of Japan(1985).

[6] T. Kamakura, M. Yoneyama, K. Ikegaya. Developments of Parametric Loudspeaker for Practical Use[J]. 10th International Symposium on Nonlinear Acoustics, Kobe, Japan(1984).

[7] F. J. Pompei. The Use of Airborne Ultrasonics for Generating Audible Sound Beams[J]. Journal of Audio Engineering Society(1999).

[8] J. James, J. O. Norris. HSS white paper[M]. USA: American Technology Corporation(2005).

[9] Dekun Yang, Stuart Flockton. An Evolutionary Algorithm for Parametric Array Signal Processing[J]. Lecture Notes in Computer Science(1995).

DOI: 10.1007/3-540-60469-3_35

[10] Furi Andi Karnapi, Woon Seng Gan, Y.K. Chong. FPGA Implementation of Parametric Loudspeaker System[J]. Microprocessors and Microsystems(2004).

DOI: 10.1016/j.micpro.2004.03.012

[11] M. Zheng, R.F.W. Coates. Angular Response of a Parametric Array: Analytical Solution[J]. Journal of Sound and Vibration(1998).