Methods for producing acoustic sources
Embodiments include an acoustic source for use in a hemi-anechoic chamber comprising a source assembly and a waveguide assembly for producing sound outside of a measurement hemisphere and channeling the sound into the measurement hemisphere. A waveguide end from which sound emanates is positioned close to the reflecting plane of the chamber and can approximate a point source.
1. A method for producing an acoustic source for use in a sound chamber having a reflecting plane and absorber-lined walls, comprising:
positioning a source assembly outside a measurement hemisphere;
coupling the source assembly to a waveguide that carries sound from the source assembly into the measurement hemisphere to emanate sound at a waveguide end; and
positioning the waveguide end from which sound emanates to be close to the reflecting plane and away from the absorber-lined walls of the chamber.
2. The method of claim 1 , wherein the height of the waveguide end above the reflecting plane is adjustable to vary the directivity of the source.
3. The method of claim 1 , wherein the source assembly is positioned on a wall that is lined with absorber.
4. The method of claim 1 , wherein the source assembly is positioned exterior to the chamber.
5. The method of claim 1 , wherein the source assembly is positioned on the reflecting plane.
6. The method of claim 5 , wherein the source assembly is covered with sound absorbing material.
7. The method of claim 1 , wherein the waveguide end is mounted near the center of the reflecting plane.
8. An acoustic source for use in a sound chamber having a reflecting plane and absorber-lined walls, the acoustic source comprising:
a source assembly positioned outside a measurement hemisphere;
a waveguide assembly coupled to the source assembly that guides sound from the source assembly into the measurement hemisphere to emanate sound at a waveguide end positionable near the center of the reflecting plane and away from the reflecting plane by an amount less than a wavelength at a highest frequency of interest.
9. The source of claim 8 , wherein the waveguide assembly further comprises a height adjustment mechanism to adjust the height of the waveguide end away from the reflecting plane.
10. The source of claim 8 , wherein the waveguide assembly comprises two or more sections of waveguide coupled by couplers.
11. The source of claim 8 , wherein a waveguide outer diameter is about a fourth of the diameter of a throat of a compression driver of the source assembly.
12. The source of claim 8 , wherein the source assembly comprises a compression driver and adapter to channel the throat of the compression driver to a smaller diameter exit aperture of the adapter.
13. The source of claim 8 , wherein the opening of the waveguide end is small enough and close enough to the reflecting plane to substantially appear to be a point source.
14. The source of claim 8 , wherein the source assembly is positioned on a wall of the chamber.
15. A method for producing an acoustic source for use in a sound chamber having a reflecting plane and absorber-lined walls, comprising:
positioning a source assembly outside a measurement hemisphere; the source assembly comprising a compression driver and adapter almost totally encompassed by sound absorbing material and with an exit aperture for coupling to a waveguide assembly;
coupling the source assembly to a waveguide assembly that guides sound from the source assembly into the measurement hemisphere to emanate sound at a waveguide end; and
positioning the waveguide end from which sound emanates to be an adjustable distance from the reflecting plane.
16. The method of claim 15 , wherein the source assembly is positioned on a wall that is lined with absorber.
17. The method of claim 15 , wherein the source assembly is positioned exterior to the chamber.
18. The method of claim 15 , wherein the source assembly is positioned on the reflecting plane.
19. The method of claim 15 , wherein the opening of the waveguide end is small enough and close enough to the reflecting plane to substantially appear to be a point source.