An apparatus and method are provided for a drone elimination muffler to attenuate drone exhibited by engine exhaust systems. The drone elimination muffler comprises a hollow canister having a length and a diameter, and a tuned port comprising a first end connected to the canister and a second end connected to the exhaust system. The canister operates in concert with the tuned port as a dampener configured to substantially attenuate exhaust drone, or resonance, at one or more frequencies of engine operation. A valve is configured to switch the drone elimination muffler between a closed state in which the exhaust system operates without acoustic influence due to the drone elimination muffler, and an open state in which the drone elimination muffler directly influences the acoustic properties of the exhaust system.

An apparatus and method are provided for a drone elimination muffler to attenuate drone exhibited by engine exhaust systems. The drone elimination muffler comprises a hollow canister having a length and a diameter, and a tuned port comprising a first end connected to the canister and a second end connected to the exhaust system. The canister operates in concert with the tuned port as a dampener configured to substantially attenuate exhaust drone, or resonance, at one or more frequencies of engine operation. A valve is configured to switch the drone elimination muffler between a closed state in which the exhaust system operates without acoustic influence due to the drone elimination muffler, and an open state in which the drone elimination muffler directly influences the acoustic properties of the exhaust system.

A valve mounting structure includes a mounting portion, a valve, and a cushion. The valve includes a valve seat having a cylindrical joining portion that receives the mounting portion inserted thereto, or is inserted to the mounting portion. The cushion is arranged between the mounting portion and the joining portion, and fixed to each of the mounting portion and the joining portion. In a case where one of the mounting portion and the joining portion is a first portion and the other is a second portion, the first portion includes a peripheral wall and an opening portion without the peripheral wall formed therein. A fixing portion in which the second portion and the cushion are fixed to each other is at least partly arranged at a position adjacent to the opening portion along a radial direction of the mounting portion.

An exhaust muffler for an exhaust system of an internal combustion engine, especially for a vehicle, includes a muffler housing with a flow volume (42), through which exhaust gas can flow, an exhaust gas inlet (28) and an exhaust gas outlet (36). A first resonator chamber (44) is open towards the flow volume (42) via a first resonator neck (68). A second resonator chamber (46) is open towards the flow volume (42) via a second resonator neck (74). A resonator pipe (52) provides the first resonator neck (68) and the second resonator neck (74).

An exhaust muffler for an exhaust system of an internal combustion engine, especially for a vehicle, includes a muffler housing with a flow volume (42), through which exhaust gas can flow, an exhaust gas inlet (28) and an exhaust gas outlet (36). A first resonator chamber (44) is open towards the flow volume (42) via a first resonator neck (68). A second resonator chamber (46) is open towards the flow volume (42) via a second resonator neck (74). A resonator pipe (52) provides the first resonator neck (68) and the second resonator neck (74).

A straddle-type vehicle comprises an engine which generates driving power and emits an exhaust gas; an exhaust device including: a catalyst which cleans the exhaust gas, an inner tube in which the catalyst is disposed and through which the exhaust gas flows, the inner tube extending to a location downstream of the catalyst; and an outer tube which covers an outer peripheral surface of the inner tube in an axial direction of the inner tube, and has a muffling space through which the exhaust gas discharged from the inner tube is flowed to reduce an exhaust noise radiated from the engine; at least one exhaust pipe through which the exhaust gas is led to the catalyst; and a downstream oxygen sensor which detects an oxygen concentration of the exhaust gas after flowing through the catalyst, at a location downstream of the catalyst in the inner tube.

A straddle-type vehicle comprises an engine which generates driving power and emits an exhaust gas; an exhaust device including: a catalyst which cleans the exhaust gas, an inner tube in which the catalyst is disposed and through which the exhaust gas flows, the inner tube extending to a location downstream of the catalyst; and an outer tube which covers an outer peripheral surface of the inner tube in an axial direction of the inner tube, and has a muffling space through which the exhaust gas discharged from the inner tube is flowed to reduce an exhaust noise radiated from the engine; at least one exhaust pipe through which the exhaust gas is led to the catalyst; and a downstream oxygen sensor which detects an oxygen concentration of the exhaust gas after flowing through the catalyst, at a location downstream of the catalyst in the inner tube.

An exhaust system for an engine has a volume element such as a muffler or a silencer. First and second exhaust pipes are connected as dual exhaust pipes upstream of or downstream of the volume element. The first exhaust pipe has a first length (L1). A valve is positioned in the second exhaust pipe at a distance (D) from the volume element. The distance D is a fraction of L1 such that the second pipe is a resonator for the first pipe with the valve in a closed position. A method of controlling exhaust noise includes positioning a valve in the first exhaust pipe at a distance (D) from a volume element with D being a specified fraction of a length of the second exhaust pipe, and closing the valve such that the first pipe provides a resonator for the second pipe to counteract standing wave in the second pipe.

An exhaust system for an engine has a volume element such as a muffler or a silencer. First and second exhaust pipes are connected as dual exhaust pipes upstream of or downstream of the volume element. The first exhaust pipe has a first length (L1). A valve is positioned in the second exhaust pipe at a distance (D) from the volume element. The distance D is a fraction of L1 such that the second pipe is a resonator for the first pipe with the valve in a closed position. A method of controlling exhaust noise includes positioning a valve in the first exhaust pipe at a distance (D) from a volume element with D being a specified fraction of a length of the second exhaust pipe, and closing the valve such that the first pipe provides a resonator for the second pipe to counteract standing wave in the second pipe.

A soundproof structure body includes a first tube structure and a second tube structure connected to the first tube structure and having a cross-sectional area different from the first tube structure, in which a structure body having a cross-sectional area smaller than a cross-sectional area of the first tube structure is installed in the first tube structure, and a transmission loss in a case where the structure body is installed in the first tube structure with respect to a case where the structure body is not installed in the first tube structure is positive at two frequencies adjacent to each other and difficult to generate an air column resonance mode in the first tube structure. This soundproof structure body generates a soundproof effect even at frequencies other than air column resonance of a tube structure such as a duct or a muffler, has a small size, and can obtain a high transmission loss in a wide-band.