| Zugriffsnummer | 10487 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Limits to the plane-wave approach in absorptive media for harmonic and transient acoustic fields |
| Autor(in); Institution |
Reibold, Rainer; 1.6, Schall, PTB-Braunschweig
|
| Quelle/Jahr | Acoustical science and technology for quality of life : proceedings of ICA 2004:(2004), V3433 - V3436 |
| Availability | [CD-ROM] ; file name: Fr2.C2.3.pdf |
| Herausgeber(in) |
International Commission for Acoustics
|
| ISBN | 4-9901915-6-0 |
| Verlag | Tokyo: ICA |
| Konferenzangaben | The 18th International Congress on Acoustics, Kyoto, 04-09, April, 2004, Japan |
| Zusammenfassung | In many types of ultrasonic investigations, we are confronted with the question as to whether or not the straightforward plane-wave approach can be reliably used for sound propagation in absorptive media or if a more complex approach should be applied. This problem is dealt with by comparing the sound field in an absorbing fluid using the plane-wave approach with that using the approach based on the Rayleigh integral and by assuming that a plane circular piston source with sinusoidal, continuous-wave and transient-wave propagation is used for sound field simulation. It is shown that both the sound field structure and the time waveform will change considerably in the presence of high absorption coefficients. A simple formula is given for the estimation of the uncertainty involved. As a general rule, for moderate frequencies and moderate transducer radius to wavelength ratios ( ƒ ≤ 10 MHz ; α / λ ≤ 50 for water; ƒ ≤ 0.1 MHz ; α / λ ≤ 30 for air and ƒ ≤ 10 MHz ; α / λ ≤ 15 for benzene), the plane-wave approach can be applied without reservation. The uncertainty between the two approaches turns out to be u rel ≤ 0.01. Care must, however, be exercised if the transducer radius is of the order of the ultrasonic wavelength (large divergence of the sound beam) or if it is much greater than the wavelength. Provided that media of a very high absorption coefficient, e. g. some biological material or oil is used, the plane-wave approach may be inadmissible especially in the Fresnel zone of the ultrasonic field. |
