UNDERSTANDING DUAL-CHANNEL FFT MEASUREMENTS.

The complexities of many engineering problems in vibration analysis and acoustics require for their solution an understanding of the cause and effect relationship existing between at least two different measurement locations. Typical examples would be in pinpointing sources of noise or vibration in an automobile or identifying the resonant frequencies and gain factors of a mechanical structure. A dual-channel FFT spectrum analyzer can be a valuable aid in establishing and measuring a cause and effect relationship. Locating and evaluating a noise source in a factory is used as an example. The dual-channel FFT functions - transfer function, coherence, and coherent output power - are valuable in separating one source from another.