Patent ID: 8256569

Claim:
A sound attenuation device for noise reduction over a wide range of frequencies emitted by the exhaust of an internal combustion engine of a motor vehicle comprising: a. a through passage having an inlet and an outlet, the inlet adapted to be acoustically coupled to pulsating sound waves emitted by said internal combustion engine and the outlet adapted to discharge the attenuated sound waves; b. the through passage comprising a tubular structure containing a plurality of perforations between the inlet and the outlet; c. a sound absorbing material surrounding the tubular structure, the density of the material being sufficiently low to allow low frequency sound waves to pass there through; and d. a frusto-conical resonant chamber surrounding and spaced from the sound absorbing material, said resonant chamber being either converging or diverging in shape and having an outer shell, said sound absorbing material located from said outer shell a distance that is one-quarter of the acoustic wavelength of frequencies to be attenuated.