Octave Analysis

What is Octave Analysis?

Octave analysis allows for the objective evaluation of sound and vibration by grouping the frequencies of an acoustic signal into “bins,” often to reflect how humans perceive the frequency spectrum.

First, the software program filters the acoustic signal and measures the sound pressure levels at the output. Then, you can apply averaging and weighting techniques in the frequency domain to correspond to the measurements of your desired evaluation of sound.

ObserVIEW Highlights

• 8th order octave band filter to meet IEC 61260-1 Class 1 filter specifications
• Automatically computes overall RMS/SPL
• Filter-based analysis with the option of FFT
• A and C frequency weighting or none (Z)
• Linear and exponential averaging
• No limit on fractional octave bands
• Configure reference values for each unit category
• Peak hold and overall RMS traces (SPL for pressure units)
• Harmonic cursor
• Supports advanced graphing capabilities, including live analysis, copy & paste, and graph traces

Filter-Based Octave Analysis

True octave analysis applies bandpass filters to the frequency range and averages each filter’s output to compute its power. ObserVIEW performs filter-based analysis as it produces more accurate results.

ObserVIEW can also use FFT data—which measures the frequency content linearly—and assign the energy to the proportional octave. This method is efficient but is only recommended if your computer cannot handle the filtered option.

Supports Any 1/N Fraction

Enter any 1/N fraction that suits your test objectives; ObserVIEW does not have a limit on fractional octave bands. (Note: there is a soft limit at 1/96 for computer performance, but you can override the limit.)

Octave Analysis Webinar

Octave Analysis in ObserVIEW

Peak Hold and Overall RMS

• Peak hold: displays the maximum amplitude for each bin over the peak hold data range.
• Overall RMS: displays the total RMS for the integration period using the selected filter (SPL for pressure units).
• Harmonic cursor: displays the trace values at each harmonic of the base cursor.

Audio Frequency Spectrum

The audio frequency spectrum is an overlay that represents the range of human hearing. Bass frequencies range from 20 to 250Hz (purple), Mids from 250 to 4kHz (yellow), and Highs from 4k to 20kHz (pink).

Data Acquisition

Vibration Research’s data acquisition systems offer the functionality to acquire and analyze acoustic signals. All VR hardware includes a BNC input that supports a microphone and is capable of data acquisition.

If your testing lab is already using VR hardware for vibration testing, sound acquisition and analysis are an economical addition.