A micromachined efficient parametric array loudspeaker with a wide radiation frequency band

Abstract

Parametric array (PA) loudspeakers generate directional audible sound via the PA effect, which can make private listening possible. The practical applications of PA loudspeakers include information technology devices that require large power efficiency transducers with a wide frequency bandwidth. Piezoelectric micromachined ultrasonic transducers (PMUTs) are compact and efficient units for PA sources [Je, Lee, and Moon, Ultrasonics 53, 1124-1134 (2013)]. This study investigated the use of an array of PMUTs to make a PA loudspeaker with high power efficiency and wide bandwidth. The achievable maximum radiation bandwidth of the driver was calculated, and an array of PMUTs with two distinct resonance frequencies (f1 = 100 kHz, f2 = 110 kHz) was designed. Out-of-phase driving was used with the dual-resonance transducer array to increase the bandwidth. The fabricated PMUT array exhibited an efficiency of up to 71%, together with a ±3-dB bandwidth of 17 kHz for directly radiated primary waves, and 19.5 kHz (500 Hz to 20 kHz) for the difference frequency waves (with equalization).

A Critical Step to Using a Parametric Array Loudspeaker in Mobile Devices

“…Many studies on signal processing techniques have been reported for improving the quality of audible sounds from the PA loudspeakers because its sound quality does not seem as good as the conventional loudspeakers [1,5]. However, it might be another good way to improve sound quality that a more adequate PA source transducer would be developed for PA loudspeaker applications [6,7]. In conclusion, the PA loudspeaker cannot yet be considered a highly successful audio source with a wide range of applications.…”

A Parametric Array Ultrasonic Ranging Sensor with Electrical Beam Steering Capability

“…Using this technique, the aperture of the source can be small compared with the wavelength of the generated sound [2]. The high directivity of the lower DFW generated by the PA makes it suitable for applications such as underwater sound navigation systems (SONAR) [ 3], high-resolution ultrasonic ranging acoustic navigation systems for mobile robots [1,4], and PA loudspeaker systems [5,6]. However, since aP Ae xploits anonlinear phenomenon, the suitability of electrical beam steering methods based on linear acoustics requires careful investigation.…”

Experimental Study of a Broadband Parametric Acoustic Array for Sub‐Bottom Profiling in Shallow Water

“…Finally, sea trials were carried out for the system, and effective detection results were obtained. While parametric acoustic array has been received considerable attention over the past decade, relatively few engineering details have surfaced about a whole broadband parametric acoustic array system [15][16][17][18][19][20].…”