Full field tomographic reconstruction of sound fields using TV holography

Abstract

A vibrating sound source causes periodic variations of the refractive index in the surrounding medium. A light wave passing through the sound field will experience a corresponding variation of its path length which can be measured by interferometric techniques like TV holography. One TV-holography recording represents the integrated optical pathlength in one direction. The sound source is rotated to record cross sections of the field as seen from different directions. By tomographic backprojection of these recordings, afterward the amplitude and phase of the sound field in any plane of the volume are reconstructed.

Acoustic Imaging of the Human Chest

“…Several algorithms are known to process multimicrophone signals. [15][16][17] However, since the distribution of sound speed and damping within the thorax is complex, known algorithms such as acoustic holography 15 and similar methods cannot be directly applied to lung sound imaging within the thorax. As time of arrival cannot be easily and unequivocally estimated for breath sounds and continuous adventitious lung sounds, algorithms relying on the measurement of time of arrival have only a limited number of applications.…”

Review of high-power ultrasound-industrial applications and measurement methods

“…Nonetheless, these devices still It should be noted that other, less popular techniques will not be covered in this article. Some of the more common ones are listed for the readers' interest: radiation pressure balances [4], holography [69], chemical detection [7], and thermal measurements [14]. Of these, thermal methods have been used with some success in high power field measurements to provide a simple means of evaluating the power in an ultrasonic cleaning bath.…”

Optical measurement of wide bandwidth ultrasound fields

“…Unifying theories have been presented explaining the relationship between Raman-Nath models and those valid for other experimental parameter ranges such as higher intensity ultrasound fields [19], higher ultrasound frequencies, and wider beam widths [20]. Later, the integrative nature of the Raman-Nath type models was exploited and tomographic techniques were used to reconstruct pressure profiles for continuous wave ultrasound beams [21][22][23][24][25][26][27][28][29][30][31][32][33].…”

“…Research on other optical methods of acoustic field measurement has been reported, particularly in air [38][39][40][41][42][43][44][45]. Among these methods are interferometric and holographic techniques [22,46]. The technique described in this paper makes only a very moderate assumption on the nature of the sound field.…”