Idle Noise Reduction of a Parametric Acoustic Array Power Driver

Matija Pirc


Parametric acoustic arrays (PAA) have progressed from specialized niche application to commercially available audio solutions in the last two decades. Their primary advantage is their incredible directivity and their main disadvantage is low conversion efficiency of the primary ultrasonic waves into audible sound. This paper presents a noise analysis of a practical implementation of a directional audio system. The system is comprised of a modulator, a D-class audio amplifier, and an emitter consisting of 97 commercially available piezoelectric ultrasonic transducers. The designed system exhibited an uncomfortable level of idle noise at the maximum volume level. The analysis of the signal path and all the noise sources revealed that the most critical component was the modulator, and a solution was devised which provided a 16 dB improvement of the carrier to noise ratio.


PAA, Parametric Acoustic Array, Directional Sound System, Ultrasonic, noise, PZT transducer

Full Text:



P. J. Westervelt, “Parametric Acoustic Array,” J. Acoust. Soc. Am., vol. 35, no. 4, p. 535, 1963,

I. Esipov, K. Naugolnykh, and V. Timoshenko, “The Parametric Array and Long-Range Ocean Research,” Acoust. Today, vol. 6, no. 2, p. 20, 2010,

S. Tang, G. Zhu, J. Yin, X. Zhang, and X. Han, “A modulation method of parametric array for underwater acoustic communication,” Appl. Acoust., vol. 145, pp. 305–313, Feb. 2019,

J. N. Tjo/tta and S. Tjo/tta, “Theoretical study of the penetration of highly directional acoustic beams into sediments,” J. Acoust. Soc. Am., vol. 69, no. 4, pp. 998–1008, Apr. 1981,

L. Kopp, D. Cano, E. Dubois, L. Wang, B. Smith, and R. F. W. Coates, “Potential performance of parametric communications,” IEEE J. Ocean. Eng., vol. 25, no. 3, pp. 282–295, Jul. 2000,

H. O. Berktay, “Possible exploitation of non-linear acoustics in underwater transmitting applications,” J. Sound Vib., vol. 2, no. 4, pp. 435–461, Oct. 1965,

L. Bjørnø, “Introduction to nonlinear acoustics,” Phys. Procedia, vol. 3, no. 1, pp. 5–16, Jan. 2010,

M. Ciglar, “Acouspade,”, [Accesed: 31. 03. 2019].

“Audio Spotlight,”, [Accesed: 31. 03. 2019].

R. Haberkern, “Soundlazer,”, [Accesed: 31. 03. 2019].

E. Hong, S. V. Krishnaswamy, C. B. Freidhoff, and S. Trolier-McKinstry, “Micromachined piezoelectric diaphragms actuated by ring shaped interdigitated transducer electrodes,” Sensors Actuators A Phys., vol. 119, no. 2, pp. 521–527, Apr. 2005,

M. Pirc and A. Levstek, “Sources of Noise in Practical Implementations of Modulators / Amplifiers for Parametric Acoustic Arrays,” in Conference 2014, proceedings / 50th International Conference on Microelectronics, Devices and Materials, October 8 - October 10, 2014, pp. 157–162.

W.-S. Gan, J. Yang, and T. Kamakura, “A review of parametric acoustic array in air,” Appl. Acoust., vol. 73, no. 12, pp. 1211–1219, Dec. 2012,

H. M. Merklinger, “Improved efficiency in the parametric transmitting array,” J. Acoust. Soc. Am., vol. 58, no. 4, p. 784, 1975,

M. Yoneyama, “The audio spotlight: An application of nonlinear interaction of sound waves to a new type of loudspeaker design,” J. Acoust. Soc. Am., vol. 73, no. 5, p. 1532, 1983,

J. J. (HSS) Croft and J. O. (HSS) Norris, “Theory, History, and the Advancement of Parametric Loudspeakers,” 2003.

“Air Ultrasonic Ceramic Transducers 400ST/R160,”

A. Levstek, “Amplitude Stabilization in Quadrature Oscillator for Low Harmonic Distortion,” Inf. MIDEM, vol. 43, no. 3, pp. 185–192, 2013.



  • There are currently no refbacks.