low frequency can be hazardous in noise pollution how to control low frequency range acoustic wave
Hi,
I`ll try an answer.
Low Frequency = longer wavelength = higher energy = less acoustic scattering
E.g. for measurements of defects in concrete pipes you often use low frequency (50kHz...200kHz) because of the inhomogeneities of material in the pipes wall. To avoid scattering you need longer wavelength. Cracks in the pipes wall result in transition to higher impedance for sound propagation and so parts of the signal will be reflected or scattered. The higher the frequency the higher the propability to hit a zone of different impedance. If the wavelength ist longer than the dimension of the obstacles then the damping of the sound wave will be lower. If the dimension of the obstacles in a material of sound propagation are close to the dimension of the wavelength then more reflection or diffraction occurs.
If you want to detect small air bubbles in water - e.g. to test leakage of pipes filled with air - then you might use higher frequency in the range of 1MHz and above to get good reflections. Hope that helps a bit.
Marc Schmieger Your answer for first part of question is helpful, May please also suggest how to control low range frequency to avoid crack propagation.Thanks
Dear Dr. Muhammad Sohaib Jarral
I agree with Marc Schmieger answer.
several publications can be found to control the low frequency noises:
some of them are here, hope be helful:
- DOI:10.1142/S2591728518500123
- DOI:10.1260/0263-0923.29.2.129
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