Sources of sound
Abstract
The properties of acoustic sources which are relevant in aerodynamic sound production namely: the monopole, dipole, and quadrupole respectively are presented. The simplest of these is the monopole, classically regarded as a small pulsating sphere. A more useful concept of the simple source, relevant to aerodynamic noise is a source of time varying mass injection. Two such simple sources, pulsating in antiphase, are combined to form a dipole. While no net mass flux exists in this situation a fluctuating force is present and represents the flow analog for dipole radiation. A combination of four appropriately phased simple sources to form a quadrupole is undertaken and shown to be equivalent to a fluctuating stress.
- Publication:
-
In Von Karman Inst. for Fluid Dyn. Advan. in Turbulent Shear Flows 20 p (SEE N79-23373 14-34
- Pub Date:
- March 1973
- Bibcode:
- 1973atsf.vkifR....M
- Keywords:
-
- Acoustics;
- Aerodynamic Noise;
- Fluid Injection;
- Radiation Sources;
- Variable Mass Systems;
- Harmonics;
- Noise Propagation;
- Pulse Amplitude;
- Spherical Waves;
- Theorem Proving;
- Fluid Mechanics and Heat Transfer