Automotive Acoustics Facilities
Test Facilities
The automotive laboratory in the Department of Mechanical Engineering at the University of Canterbury has both an engine test cell with a computer controlled engine dynamometer and a rolling road test facility. The test facilities are currently being used to investigate the performance of resonant ty
pe automotive mufflers. The layout of the automotive laboratory is shown in attachment 1. In order to facilitate testing of automotive muffler systems the exhaust system from a Toyota 3S-GE engine was passed through the wall from the engine test cell (source room) to the rolling road room. In the rolling road room (hereafter referred to as the receiving room) a false floor was constructed to simulate the tailpipe height of a standard passenger cars exhaust system. The test layout and test engine specifications are shown in attachment 2.
A number of tests have been performed to quantify the acoustic environment of the test facilities including the reverberation time of the receiving room and the transmission loss of the wall between the engine test cell and the receiving room. These tests allowed the lower cutoff frequency of the receiving room, that is the frequency to which the room can be considered semi-anechoic, to be determined as approximately 100 Hz. These measurements also allowed the background noise present in the receiving room due to the engine running in the test cell to be determined.
Muffler system performance can be determined using the test engine running at set speeds and loads or by setting controlled engine sweeps. Muffler system performance can also be quantified using a speaker as a source of excitation. An anechoic termination is also available to allow the performance of single muffler components to be determined. The rolling road can be utilised to perform measurements with running vehicles stationary under load to investigate various noise and vibration issues.
Measurement equipment
The automotive laboratory has computer controlled dynamometer facilities allowing the data logging of engine speed and output. Pressure measurements can be made both in cylinder and in the exhaust system itself using water cooled high performance piezoresistive pressure transducers. Data can be acquired from pressure transducers simultaneously using a 16 channel data acquisition system (up to 10 kHz sampling). Axial temperature gradients through the exhaust system can be measured using K-type thermocouples allowing temperature measurement up to 1400°C. Vibration measurements can be made using a range of accelerometers and a dual channel Polytec laser doppler vibrometer. Sound measurements can be made using a Brüel and Kjær sound measurement system.
Figure 1 - Automotive Laboratory layout (dimensions in meters)
Figure 2 - Detail of wall between source and receiving room
Rolling road room properties
Surface Area: 212 m²
Volume: 171 m³
Figure 3 - Exhaust system details
Table 2 - Toyota 3S-GE test engine specifications
Engine Model |
3SGE II |
Bore |
86 mm |
Stroke |
86 mm |
CC rating |
1998 |
Compression Ratio |
10.0:1 |
Cylinder Angle |
50° |
Brake Horse Power |
156 @ 6600 RPM |
Torque (lb ft) |
137 @ 4800 RPM |