On response measurements using deterministic types of periodic signal and FFT

Auteurs-es

  • W.T. Chu Acoustics Lab., Inst. for Res. in Construction, Nat. Res. Council Canada, Ont., Canada

Mots-clés :

acoustic signal processing, acoustic variables measurement, fast Fourier transforms, FFT analyzers, aliasing, leakage, picket fence effects, random errors, periodic signals, system response measurements, dual channel A/D converter

Résumé

System response measurements appear in many areas of scientific and technical investigations. The speed of these measurements has been greatly improved with the advent of FFT analyzers. Conventional FFT analyzers require two channels to measure the system response using white noise as a stimulus. Bias errors such as aliasing, leakage, and picket fence effects have to be properly addressed and random errors have to be minimized by averaging. Uses of deterministic types of periodic signal as stimulus are not common although most of these errors would disappear. The inflexibility of the commercial FFT analyzers may be an important reason. To analyze periodic signals, it is necessary to use an `exact' multiple of the period of the signal to avoid leakage effect. It is also necessary to ensure that the signal frequencies coincide `exactly' with the analysis frequencies to avoid picket fence effect. This will require some tailoring of the sampling frequency and the number of data points. We explore the application of deterministic types of periodic signal for system response measurements using a dual channel A/D converter and a special FFT routine. Two types of periodic signal are discussed: (1) pure tones for single frequency measurements and (2) m-sequence or maximum-length sequence (MLS) for broadband measurements

Fichiers supplémentaires

Publié-e

1994-09-01

Comment citer

1.
Chu W. On response measurements using deterministic types of periodic signal and FFT. Canadian Acoustics [Internet]. 1 sept. 1994 [cité 30 avr. 2026];22(3):45-6. Disponible à: https://jcaa.caa-aca.ca/index.php/jcaa/article/view/842

Numéro

Vol. 22 No. 3 (1994)

Rubrique

Actes du congrès de la Semaine canadienne d'acoustique

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