Estimation of ultrasound attenuation and dispersion using short time Fourier transform

• Published in: Ultrasonics 2005-03, Vol.43 (5), p.375-381
• Main Authors: Zhao, B., Basir, O.A., Mittal, G.S.
• Format: Article
• Language: English
• Subjects: Acoustical measurements and instrumentation; Acoustics; Algorithms; Attenuation; Biological and medical sciences; Computer Simulation; Exact sciences and technology; Fourier Analysis; Fundamental areas of phenomenology (including applications); Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; Models, Theoretical; Phase velocity; Physics; Short time Fourier transform; Time Factors; Transducers; Ultrasonic investigative techniques; Ultrasonics, quantum acoustics, and physical effects of sound; Ultrasonography - methods; Ultrasound
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/j.ultras.2004.08.001

Determination of the acoustic attenuation and dispersion has important applications in ultrasound tissue characterization and non-destructive material testing. Current signal processing methods Fourier transform of ultrasound signals to get the spectra of amplitude and phase to estimate respectively the attenuation and dispersion of a given medium. These methods are frequency domain method and obsessed with ambiguity issue in the phase unwrapping calculation. Conventional ultrasound velocity measuring method detects the time of arrival of a pulse (or echo) signal, which is a time domain method to compute group velocity (not phase velocity). This paper presents a novel approach based on the short time Fourier transform (STFT)—a time-frequency analysis, to estimate the ultrasonic dispersion and attenuation. Only the amplitude information of the pulse-signal spectra is used. Based on the time-frequency presentation, the attenuation coefficient of the signal is obtained by computing the amplitude decay of pulse spectrum in time domain, while phase velocities are obtained based on the “time–of–flight” (TOF) of the mono frequency component of the pulse signals. As a result, we eliminate the ambiguity issue in phase angle calculation. Furthermore, the proposed method makes the phase velocity pedagogically intuitive for novice users. The paper presents experiments to evaluate demonstrate the performance of the proposed method.