| Autor: |
Tony D. Heathershaw, Timothy G. Leighton, Niven R. Brown, S.D. Richards |
| Rok vydání: |
1998 |
| Předmět: |
|
| Zdroj: |
The Journal of the Acoustical Society of America. 103:2900-2900 |
| ISSN: |
0001-4966 |
| DOI: |
10.1121/1.422034 |
| Popis: |
The visco‐thermal absorption of sound by suspended particulate matter can be reliably measured using a reverberation technique. This absorption may have an adverse effect on the performance of sonars operating at low ultrasonic frequencies in coastal waters where suspensions are often present in significant concentrations. A series of experiments has been performed to study the viscous absorption by suspensions in the frequency range of 50–150 kHz by taking the difference in reverberation times of a volume of water with and without particles. Measured attenuation agrees reasonably well with that predicted by theory for concentrations above 0.5 g/l. A number of interesting phenomena have also been observed which are related to the measurement system and the turbulent flow required to keep the particulate suspended. For accurate measurement, losses at the container walls must be minimized. Although there are small losses at the surface by transmission, along with losses due to absorption in the acoustic boundary layer, the presence of bubbles and dissolved gas, and turbulence, the relative measurement gives a good assessment of the absorption by the particles. These effects are discussed and results for particulate absorption are presented. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
|
