Pressure-sensitive paint as a distributed optical microphone array

Abstract

Pressure-sensitive paint is presented and evaluated in this article as a quantitative technique for measurement of acoustic pressure fluctuations. This work is the culmination of advances in paint technology which enable unsteady measurements of fluctuations over 10 kHz at pressure levels as low as 125 dB. Pressure-sensitive paint may be thought of as a nano-scale array of optical microphones with a spatial resolution limited primarily by the resolution of the imaging device. Thus, pressure-sensitive paint is a powerful tool for making high-amplitude sound pressure measurements. In this work, the paint was used to record ensemble-averaged, time-resolved, quantitative measurements of two-dimensional mode shapes in an acoustic resonance cavity. A wall-mounted speaker generated nonlinear, standing acoustic waves in a rigid enclosure measuring 216 mm wide, 169 mm high, and 102 mm deep. The paint recorded the acoustic surface pressures of the (1,1,0) mode shape at approximately 1.3 kHz and a sound pressure level of 145.4 dB. Results from the paint are compared with data from a Kulite pressure transducer, and with linear acoustic theory. The paint may be used as a diagnostic technique for ultrasonic tests where high spatial resolution is essential, or in nonlinear acoustic applications such as shock tubes.

Reconstruction of surface-pressure fluctuations using deflectometry and the virtual fields method

“…As PSP is a technique for the measurement of absolute pressure, it is generally difficult to resolve small differential amplitudes (Beverley and McKeon 2007, chapter 4.4). Using phase averaging to address the restricting factor of camera noise, as well as a porous paint formulation, acoustic pressure amplitudes of down to 500 Pa were measured in Gregory et al (2006). Using phase averaging in combination with proper orthogonal decomposition to measure the interaction between a rotor wake and a cylinder, PSP measurements of fluctuations within 100 Pa were achieved with good agreement to microphone measurements in Jiao et al (2019).…”

Visualization of the Mode Shapes of Pressure Oscillation in a Cylindrical Cavity

“…While methods for both numerical and analytical solutions have been developed to obtain natural frequencies and mode shapes of acoustic resonance in cavities with different shapes (Blevins, 1979;Dowling, 1995;Dowling and Stow, 2003;Hong and Kim, 1995;Kim and Soedel, 1989;Lee, 2011;Mirsky, 1965aMirsky, , 1965b, experimental studies were mostly limited to natural frequencies based on local pressure measurement (Hickling et al, 1983;Payri et al, 2005;Stanković and Böhme, 1999). Only a few studies have been conducted to visualize the mode shapes in cavities using microphone measurements (Gregory et al, 2006;Mamede and Varoto, 2003) and Schlieren measurements (Chinnery and Humphrey, 1996). Resonant frequencies and mode shapes of plates were also visualized using electronic speckle pattern interferometry (Huang, 2002;Mirza et al, 2006).…”

Dynamic and Steady Characteristics of Polymer-Ceramic Pressure-Sensitive Paint with Variation in Layer Thickness

“…Polymer-ceramic PSP (PC-PSP) has been investigated to satisfy both the fast response and spraying characteristics [22,23,24,25,26]. This PSP uses both a porous material and polymer as a supporting matrix (Figure 2).…”