Sonic infrared (SIR) imaging is an original hybrid nondestructive evaluation (NDE) technique that has seen rapid acceptance in the industry. A single-tone ultrasonic wave in the 15–40 kHz range is induced to the specimen under inspection through a high-power ultrasonic plastic welder. Heating duration is equal to the ultrasonic excitation duration. In a previous article, an analytical model for depth profiling using SIR NDE was presented. According to the proposed model, material thermal properties, defect size and ultrasonic excitation duration influence defect characterization and contribute to the total temperature-time curves. In this paper, heating duration effect on the quantitative estimation of flaws using sonic infrared nondestructive evaluation was investigated.