PULSE Reflex Standardised CPB Option Type 8706

Constant percentage bandwidth (CPB) 1/nth octave analysis is a useful and computationally efficient method for characterising the amplitude of sound or vibration energy as a function of frequency. It is especially useful in acoustic applications, as its logarithmic frequency scale is well suited to the characteristics of the human ear - which responds to pitch changes in ratios rather than actual frequencies. Broadband noise or vibration is more easily quantified and compared using CPB spectra than narrow band FFT spectra.

Uses

• General acoustic analysis
• 1/nth octave analysis of sound and vibration data
• Energy distribution as a function of frequency
• Frequency band level as a function of time or RPM

Features

• 1/n^th octave analysis to IEC, DIN and ANSI standards
• N = 1, 3, 6, 12 and 24
• 1/n^th octave  spectrum, linear or exponential averaging
• Exponential averaging – includes Slow (1s) and Fast (1/8^th s) modes, but covers a tau range from 1/2048^th  s to 512 s
• Overall weighted or unweighted level (A, B, C, or D weighting)
• 1/n^th octave level versus time (via frequency band extraction)
• 1/n^th octave spectrum versus time
• 1/n^th octave spectrum versus RPM (in conjunction with Type 8704)

A standard CPB display showing two signals overlaid.




CPB spectra can be displayed as a function of time. The red bars indicate total A-weighted and linear sound pressure levels for the CPB spectrum lying under the cursor.


In PULSE Reflex Core, CPB spectra can be mapped as a function of time. The option to map against speed is provided in combination with PULSE Reflex Core Basic Order Analysis Type 8704.




CPB spectra can be displayed as a function of RPM (requires a license for Type 8704).