The measurement and analysis of sound waves traveling in air, solids and liquids is important to a number of industries involved in production test, machine/engine performance and process control. Signals detected by sensors such as microphones and accelerators can reveal critical information about an objects behavior and action. Sound waves can also be used for acoustic location with active techniques employing sound generation and studying echo responses while passive methods listen for generated sounds or vibrations and then endeavor to determine the direction and location of the source. Perhaps the most famous acoustic location method is SONAR where hydrophones are be used to monitor waveforms traveling in water. However, acoustic location is also employed in other mediums and plays a key role in material science and geology.
Using the latest PC based technology, Spectrum digitizers and arbitrary waveform generators make excellent tools for use in the development, testing and operation of acoustic systems. Small and compact they offer a wide range of bandwidths and sampling rates so that they can best match the measurement needs. High-resolution digitizers offer 16 bit performance with very high precision and low noise. The cards deliver outstanding signal-to-noise ratio's (up to 90 dB) and spurious free dynamic range (up to 115 dB) so that the smallest signal variations can be detected and analyzed. Dynamic range is further extended by a front-end design which provides up to eight different full scale ranges (from ± 50 mV up to ± 10 V) and wide input offset.
Each digitizer card can have from one to sixteen channels and up to sixteen cards can be linked together with Spectrum's StarHub system to create instruments with up to 256 fully synchronous channels making them suited to applications with multiple sensors and sensor arrays. If necessary even larger systems can be created by connecting StarHub systems together making it possible to build systems with thousands of fully synchronized channels. The cards also come with large on-board memories (up to 1 Gsamples/card) and advanced streaming and readout modes for capturing and transferring signals. Streaming over the cards fast PCIe or PCI bus to a RAID based storage array allows the capture and storage of days of information. Spectrum's S Bench 6 software can also be used to view and qualify signals. FFT's are available for frequency domain analysis and power measurements while parametric calculations help to determine key signal characteristics like amplitude, frequency, pulse width and period.
Typical acoustic applications include acoustic ranging, acoustic location, SONAR, seismology, acoustic emission, vibration analysis, engine testing, process control, ocean acoustic tomography and bio-acoustics.
Spectrum Product Features
- Sampling rates up to 5 MS/s
- Differential inputs
- Very low SNR and SFDR
- 8 input ranges from ±50 mV to ±10 V full scale
- Segmented Memory with FIFO Readout
- Star-Hub for high channel count systems with full synchronization
- SBench 6 for control display and analysis
Matching Card Families
5 MS/s - 125 MS/s
40 MS/s - 125 MS/s
Mechanical Measurements Using Digitizers
Measurements on mechanical devices and systems using a modular digitizer requires the use of a variety of transducers or sensors in order to convert mechanical parameters such as force, acceleration, pressure, rotational speed, and their kindred into electrical signals you can measure. This article is a primer on making such measurements using a modular digitizer.
Case Study: Time Reversal Focusing
The ability to focus waves offers interesting possibilities in a number of fields such as communications, ultrasound, nondestructive testing (NDT), medical science and audio. For example, in biomedical applications, focused ultrasound can be used in lithotripsy procedures for treating kidney stones or to target brain tumors. Similarly in NDT, the TR process has been used to help locate and characterize defects in solid materials. In addition, it can be used to create high amplitude focusing of ultrasound for a non-contact source used for nondestructive evaluation.
Signal Processing for Digitizers
Modular digitizers allow accurate, high resolution data acquisition that can be quickly transferred to a host computer. Signal processing functions, applied in the digitizer or in the host computer, permit the enhancement of the acquired data or the extraction of extremely useful information from a simple measurement.
Case Study: Sound waves studied in a simulated ocean with high-precision PCIe measurement cards
The Acoustics Research Group at the Department of Physics and Astronomy, Brigham Young University, Utah, USA has chosen Spectrum Instrumentation’s leading-edge digitizers and signal generators to form the heart of its new underwater acoustics laboratory. The new lab is a big step forward in research on sound waves travelling through water as it effectively provides a miniaturized version of the ocean. Experiments are possible on sound wave’s behaviour in different water layers and their reflections from the ocean’s most diverse ground materials such as rocks, sand or mud. The miniaturization means that the highest precision is needed from the measurement equipment as the experimental results are scaled up afterwards to indicate what would happen in the real world.
At the Shandong University, School of Mechanical Electrical and Information Engineering, Weihai, China they are using acoustic emission together with the model M2p.5922-x4 20 MS/s, 16-bit Digitizer to detect broken wires in bridge cables. Details of the research can be found belowResearch Paper
See how Shanghai University of Engineering and Science, Shanghai, China, use Acoustic Emission techniques to study tensile fracture in polyester and cotton with a Spectrum digitizer M2i.4911-exp (this article is in Chinese) by clicking here:Research paper (Chinese)
Underwater Acoustics Laboratory
A new underwater acoustics laboratory has been created at Brigham Young University, Utah, in the US. For sensor positioning, signal generation, and data acquisition they are using Spectrum Instrumentation M2p.6546-x4 and M2p.5932-x4 40 MS/s, 16-bit AWG and Digitizer cards. A white paper describing the lab setup, including details about the water tank, water treatment and sanitizer system, anechoic panels, signal transmission and data acquisition, and the automated positioning system can be found hereWhite Paper
Acoustic horn characterization
The National Defense Academy, in Japan are investigating source of acoustic cavitation noise from bubble clusters under ultrasonic horns. Their research uses a hydrophone and schlieren visualization together with an M4i.4451-x8 500 MS/s, 14-bit Digitizer to help determine the horns characteristics for direction, autocorrelation and frequency. A research paper discussing the work can be found here:Research Paper