• 소음진동
• /
• 제9권5호
• /
• pp.943-948
• /
• 1999

This paper proposes a feasible and effective method for measuring the mechanical-acoustic transfer function by the application of equivalent area and velocity transfer function, a manifestation of the vibro-acoustical reciprocity principle. On the contrary to the volume velocity used in traditional method, the equivalent area is a peculiar raidation characteristics of sound sources and not influenced by any input signal for driving sound source. This invariant property of equivalent area can get rid of boresome works to measure the volume velocity of a sound source every time the driving signal is changed. Moreover, this method has a remarkable advantage to use a general loudspeaker as an accoustic exciter without the assumption of point source and can be applied to all kinds of sound sources even if they are not omni-directional sources.

• 소음진동
• /
• 제9권4호
• /
• pp.822-827
• /
• 1999

The reduction of booming noise level and improvement of sound quality in the vehicle interior have been major fields of vehicle NVH for many years. In order to reduce the booming noise this paper proposed a system variable, which takes account of mode shapes and natural frequencies of the structural-acoustic system, measurement points and excitation frequency. By simplifying the system variable, the major contributors of panels inculding roof, roof lining, wind shield glasses, doors and floor to booming noise at a specific frequency was experimentally found. Also the relationships between structural modes of roof lining, one of the major contributors, and acoustic modes of compartment cavity were investigated from the viewpoint fo structure-borne noise. In addition, the roof lining was modified structurally by applying marble sponge to the gap between roof and roof lining. Asthe result of structural modification, the booming noise was reduce at target frequency.

• 한국소음진동공학회논문집
• /
• 제19권1호
• /
• pp.42-49
• /
• 2009

In this paper, an alternative method was introduced to conduct a transfer path analysis for airborne noise. The method used the transfer function matrix composed of acoustic transfer functions that are referenced by the input voltage of a calibration source. A calibration factor which is converting a virtual voltage to source strength was deduced by vibro-acoustical reciprocity theorem. The calibration factor is then multiplied to the virtual input voltage to estimate the operational source strength. Three loudspeakers were used to noise sources of acrylic half car model. The method was applied to airborne noise transfer path analysis of the half car. The estimated source strength by transfer path analysis was compared the deduced source strength by vibro-acoustical reciprocity to verify the method.

• 한국자동차공학회논문집
• /
• 제7권9호
• /
• pp.158-164
• /
• 1999

In this paper a simple measurement technique for mechanical-acoustic transfer functions is proposed . The mechanical-acoustic transfer functions, generally , are measured through mechanical excitations ; impact hammers or shakers. Recently , by virtue of vibro-acoustical reciprocity principle, they are measured through acoustic excitations : loudspeakers. This kind of test needs to measure the volume velocity , the radiation characteristics of a sound source. Because the volume velocity of the sound source is changed by driving signal , it is difficult to measure it. However , the new method in this paper needs not to measure the volume velocity of a sound source by combination of mechanical and acoustic excitations. Moreover, this method has the methodological advantages, such as usage of a general loudspeaker for the reciprocal excitation, no sptatial limitations for measurements of mechanical-acoustic transfer functions.