Impedance tube, Kundt’s tube, sound absorption and transmission loss
The impedance tube (also know as Kundt Tube) measurement obtains the normal incidence absorption coefficient of a layer of textiles with a small diameter (usually less than 10 cm).
The results can be used to compare the basic absorption performance of the material and for acoustics simulations.
In practice, the absorbers can be quite large and their structure and configuration may be complex and part of acoustic designs. Furthermore, they will be exposed to real sound fields where the incident sound may come from many directions.
The PLACID impedance tube kit consists of 2 tubes with a diameter of 30 and 100 mm to cover the whole frequency range. At the end of the tube, a loudspeaker is mounted and will emit a precisely quantified sound generated by the signal generator and amplified by the amplifier.
The microphones will measure the sound level at each given position. The software will then calculate the normal incident acoustic properties of the material based on the frequency response functions measured between the various measurement locations.
The Impedance tube kit can determine the sound absorption coefficient as well as the transmission loss.
PI8810, 100 mm impedance tube, frequency range 63 Hz – 1600 Hz
PI8803, 30 mm impedance tube, frequency range 800 – 6300 Hz
Impedance tube can measure sound absorption coefficient as well as transmission loss, ISO10543-2, ASTM E1050-08.
.Microphones used: 1/4″ Class 1, 20 Hz to 20 kHz (BNC to SMB connector)
Applications for Impedance Tube
- testing of material characteristics and verifying material compliance before implementing the materials in the assemblies
- design of acoustic comfort in aircraft, helicopters, ships, yachts and vehicle interiors by selecting the optimal acoustic treatments and noise barriers
- research and development of noise control products by benchmarking competitive products
- research jobs for students and universities
- validating and calibrating theoretical computational methods such as acoustic modelling
Define material Characteristics
Materials in acoustic application typically either are used for sound absorption or for noise transmission loss. Acoustic designers need to know the exact noise characteristics of a material to be able to make predictions. Testing a material in the Impedance Tube is quick and precise.
Measurement microphone cartridges for Soundlevel meters & IPE
Placid PMP20 Class 1 microphone
PMP20, Class 1 microphone, 0 Volt polarization voltage, free field, 20 Hz – 40 kHz
Standard (IEC61672): Class 1
Measuring method: Free field
Frequency response: 20 – 40 kHz
Calibrator for sound level meters, 1 kHz, levels 94 dB and 104 dB. Can be used for any sound level meter with a 1/2″ microphone.
PLACID CA-02 calibrator features:
- sound calibrator with 2 levels, 94 dB and 104 dB at 1 kHz
- Accurate and very easy to use
- can be used for calibration of 1/2″ and 1/1″ microphones
- low battery indicator
- complies with IEC60942: 2003, Class 2
- complies with ANSI S1.40
PLACID CA-02 calibrator specifications:
- Output Sound Pressure Levels: 114dB and 94dB re 20 uPa under reference Conditions
- Output Frequency: 1000Hz ±2%
- Total Harmonic Distortion: < 4%
- Reference Conditions:
Static press 103hpa
Relative humidity 50%
- Accuracy of sound pressure level:
Understated reference environment conditions ±0.5dB
- Battery test:
Operate: Green LED indicator
Low battery: Red LED indicator
- Battery: 9 Volt battery
- Dimensions: 115 x 65 x 45 mm
- Weight: Approximately 170g
SoundPower Hemisphere kit for measurements ISO3744, ISO3745
PLACID HS10 / HS20
Frequency range: 3.15 Hz to 20 kHz
Dynamic range: 17 dB to 139 dB
Sensitivity: 50 mV/Pa
Measures incl. feet: Diagonal 1500 mm
# of Microphones: 10 or 20 1/2″ microphones
PLACID HS10 – HS20, the hemisphere will hold either 10 or 20 microphones according to the relevant used standards. Easy assembly and packing.