Study on the Monolithic Muffler Acoustic Field Performance of the Train Air-Conditioning - Advanced Research on Computer Education, Simulation and Modeling - page 142

3 Validation and Performance Analysis of the Muffler Acoustic
Field Simulation
3.1 Tests on the Muffler Sound Field Performance
In order to verify the correctness and rationality of the muffler sound field model, we
do the measurement on the test-bed of train air-conditioning duct. Fig. 2 shows
test-bed schematic diagram. Testing instruments is as follow:
Fig. 2. Test-bed schematic diagram
(1) The polyhedron sound sources, it is the sound source without directivity which
adopts electric speakers and it is usually used in the architectural acoustics test as
point source. In the 100-10000Hz frequency range, the sound power of center
frequency of all 1 / 3 octave changes within the 12dB and the sound power level of
the center frequency of the two adjacent 1 / 3 octave changes within ± 3dB.(2) The
microphone, its function is to convert acoustic signals into electrical signals. (3)The
dual-channel acoustic real time analyzer, it is a digital frequency line display device,
it can display simultaneously the input signal within its measure range in a very short
period of time, it connects microphone probe by two channels interface, and can real-
time measure A, B, C weighted sound level in octave band and 1 / 3 octave Zones,
and shows the obtained data in order to facilitate to analysis further. (4) The sound
calibrators, it is a sound source that can produce a constant level value for 94dB under
the frequency of 1000HZ ,and can be used to calibrate the absolute sound pressure
sensitivity of the microphone. We must calibrate the microphone before and after the
measurement. (5) The power amplifier.
Firstly open air conditioning unit, and adjust the air supply fan for 3800m 3 /h to test
the flow field, including the upstream and downstream flow of the muffler, static
pressure, dynamic pressure and temperature tests. Turn off air conditioning unit After
the flow field test, open the acoustics test instrument and debug the acoustic power
amplifier, while ensure the interior noise value of the train greater 10dB than
background noise value, then may begin the acoustic test.