Acoustic sensors and signal acquisition

The function of the acoustic sensor in the Impulse Excitation Technique is to capture the specimen acoustic response. The sensor must be directional and have high immunity to ambient noise to facilitate frequency identification. Sonelastic® Systems have two options of directional sensors for frequencies up to 96 kHz that meet this requirement.

To the Sonelastic® Software process the acoustic sensor signal, it must be digitized by an acquisition device. For this function, Sonelastic® Systems have precision options with sampling rate compatible with the typical systems frequency ranges.

It is important that the acoustic sensor and acquisition device to be calibrated with traceability to the International System of Units (SI) with regards to frequency measurement. Frequency is the main parameter for the determination of elastic moduli in the Impulse Excitation Technique.

Acoustic sensor

ATCP Physical Engineering, Sonelastic® Division, developed and manufactures acoustic sensors specific for the Impulse Excitation Technique. Model CA-DP and CA-DP-S sensors are directional and capable of detecting frequencies within the 70 Hz - 96 kHz range. The CA-DP-S model has a smaller diameter (8 mm) end for easy placement on small-sized specimens.

Acoustic sensor model CA-DP-S (top in the first picture and in the second) and the model CA-DP (bottom in the first picture and in the third one).

The acoustic sensors use a 3.5 mm TRS P2 connector compatible with the USB module ADAC, the XONAR card, and most commercial audio acquisition cards.

Specifications
Models and respective tip diameters: CA-DP (12.7 mm) and CA-DP-S (8.00 mm);
Transducer element: Dedicated electret;
Frequency range: 70 Hz - 96 kHz;
Sensitivity: -40 dB ±8 dB (0 dB = 1 V/Pa);
Directivity: -10 dB at 90° @ 1 kHz / 1 cm;
Signal-to-noise ratio (S/N): ≥56 dBA.

Signal acquisition

Sonelastic® Systems have two options for signal acquisition. The first one is the signal acquisition USB module ADAC, for the frequency range from 20 Hz to 22.5 kHz. The ADAC was developed and manufactured by ATCP Physical Engineering, Sonelastic® Division and is typically used in systems for medium and large specimens with low and medium frequencies (up to 22.5 kHz).

Signal acquisition USB module ADAC (first image) and its typical spectrum when digitizing a monotonic 22.5 kHz signal.

The second option is the signal acquisition PCIe card XONAR, compatible with the PCIe bus of desktop computers and for the frequency range of 20 Hz to 96 kHz. The XONAR card is manufactured by ASUS company and is typically used in systems for small samples with high frequency (up to 96 kHz).

Signal acquisition PCIe card XONAR (first image) and typical spectrum when digitizing a monotonic 87 kHz signal.

We are able to supply Sonelastic® Systems with calibration certificate traceable to the International System of Units (SI).

Signal acquisition USB module ADAC (first image) and its typical spectrum when digitizing a monotonic 22.5 kHz signal.

The calibration certificate is for the set formed by an acoustic sensor and a module or signal acquisition card. In the case of the XONAR board, the calibration is should be carried out with the card installed in system computer.

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