![]() ![]() The highest frequency that a healthy ear can typically hear is 2.0 x 104 Hz. However, even high frequency sound waves exhibit much more diffraction under normal circumstances than do light waves that pass through the same opening. For example, the wavelength at 250Hz is close to 1.37 meters (4.5ft) long. Chapter 27, Problem 23 High-frequency sound waves exhibit less diffraction than low-frequency sound waves do. Conditions are free-field and there is no reverberant field. At low frequencies, up close to the sound sourcetechnically very near-fieldwe are actually dealing with a point source, since sources tend to be much smaller than the wavelength of low-frequency soundwaves.Diffraction of waves by a dielectric parabolic cylinder. Walls used in the model are considered to be perfectly reflecting and at 1 metre distance (facade level). Diffraction Low-Order Filter Approximation of Diffraction for Virtual Acoustics Authors: Christoph Kirsch Carl von Ossietzky Universität Oldenburg Stephan D. Thus for a given barrier thickness the low frequency sound is transmitted more than the high.The noise source behaves as a point source and is far-field, where inherent directivity is minimal.There are no affecting weather conditions, such as wind or temperature inversion, as these will affect the propagation path of a noise source and diffraction around the barrier.In reality when dealing with short distances and many reflective surfaces the "canyon effect" may occur with repeating reflections. There are no reflections from the barrier. This is important because a long wavelength means that the sound wave can pass around barriers, like rocks, easily.No transmission of sound through the barrier - therefore, the total transmission of sound through the barrier must be at least 10dB below the level of sound transmission above the barrier.No transmission of sound around the barrier - therefore, the combined transmission of sound around the sides of the barrier must be at least 10dB below the level of sound transmission above the barrier. Could anyone explain to me why low frequency sounds diffract better than high frequnecy sounds around a corner (eg the wall of a building). ![]()
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