Octave Band Analysis and Analyzer

Octave band analysis is an indispensable tool for sound measurement because it gives a close approximation of how the human ear responds. Dewesoft octave band analyzer meets all of the IEC and ANSI specifications for octave filters.

Octave Band Analysis solution from Dewesoft
IEPE
IEPE
Voltage
Voltage
FlexRay
FlexRay
Video
Video
Sound
Sound
Sound pressure
Sound pressure

Highligts

  • TRUE OCTAVE ANALYSIS: true octave filters exactly represents the filter sets defined by the IEC 61260 standards and give the user real-time response for vivid live visualization of data, crucial for advanced acoustic analysis
  • SYNTHESIZED ANALYSIS: for large channel count systems Dewesoft provides extremely fast calculation from frequency domain
  • SEAMLESS ACOUSTIC SUITE INTEGRATION: octave analyzer is perfectly integrated with sound level, sound power, sound intensity and other modules for advanced sound analysis
  • RESOLUTION UP TO 1/24 OCTAVE: for deep analysis of data Dewesoft provides very narrow band analysis up to 1/24th octave
  • FREQUENCY SOUND WEIGHTING: standard frequency weighting curves (A, B, C, D and Z) can be applied directly in a frequency domain for analysis of sound
  • FREQUENCY AVERAGING: block history with linear, peak, exponential averaging or overall calculation is available.
  • LIFETIME FREE SOFTWARE UPGRADES AND SUPPORT: Our data acquisition systems come bundled with award-winning Dewesoft X data acquisition software. The software package is always evolving and new features are being added. We offer lifetime FREE software upgrades and technical support to all our users.

Constant Percentage Bandwidth (CPB)

CPB filter is a filter whose bandwidth is a fixed percentage of a centre frequency. The width of the individual filters is defined relatively to their position in the range of interest. The higher the centre frequency of the filter, the wider the bandwidth.

The widest octave filter used has a bandwidth of 1 octave. Many subdivisions into smaller bandwidths are often used. The filters are often labeled as “Constant Percentage Bandwidth” filters. A 1/1-octave filter has a bandwidth of close to 70% of its centre frequency. The most popular filters are perhaps those with 1/3-octave bandwidths. One advantage is that this bandwidth at frequencies above 500 Hz corresponds well to the frequency selectivity of the human auditory system. DEWESoft supports up to 1/24-octave bandwidth.

Constant Percentage Bandwidth (CPB)

Calculation Principle

True octave(ANSI, IEC)

Uses filter sets as in analog octave analyzers. One of the main advantages is that we can really see the dynamic behavior of the input data.

Synthesized

Calculated using FFT as the base and is updated when every FFT is being calculated.

Calculation Principle

Frequency Weighting

Frequency weighted noise measurements offer standard ways to measure sound, and we use each of these frequency weightings for different types of measurements.

  • A-weighting is applied to measured sound levels in an effort to account for the relative loudness perceived by the human ear. The human ear is less sensitive to low and high audio frequencies.
  • B-weighting is the best weighting to use for music listening purposes.
  • C-weighting is used for high-level noise measurements.
  • D-weighting was specifically designed for use when measuring high-level aircraft noise in accordance with the IEC 537 measurement standard. The large peak in the D-weighting curve reflects the fact that humans hear random noise differently from pure tones, an effect that is particularly pronounced around 6 kHz.
  • Z-weighting is linear at all frequencies and it has the same effect on all measured values.
Frequency Weighting

Averaging Type

Averaging is used to get more stable results. There are three averaging modes available:

  • Linear averaging - each FFT counts the same
  • Exponential averaging - FFT’s become less and less important with time
  • Peak hold averaging - only maximum results are stored and shown

 

Averaging Type

FAQ

What is Octave band?

An octave band is a frequency band that spans one octave. In this context, an octave can be a factor of 2 or a factor of 100.3. 2/1 = 1200 cents ≈ 100.301. Fractional octave bands such as 1⁄3 or ​1⁄12 of an octave are widely used in engineering acoustics.

Octave band analysis is often used in noise control, hearing protection and sometimes in environmental noise issues.

What is octave band analyser?

Real-time octave band analyzers are special sound level meters that divide noise into its frequency components. Electronic filter circuits are used to divide the sound or noise into individual frequency bands.

Dewesoft offers flexible octave band analyzers for any sound measurement.

What is constant percentage bandwidth (CPB) filter?

CPB filter is a filter whose bandwidth is a fixed percentage of a center frequency. The width of the individual filters is defined relative to their position in the range of interest. The higher the center frequency of the filter, the wider the bandwidth.

The widest octave filter used has a bandwidth of 1 octave. Many subdivisions into smaller bandwidths are often used. The filters are often labeled as Constant Percentage Bandwidth filters.

A 1/1-octave filter has a bandwidth of close to 70% of its center frequency. The most popular filters are perhaps those with 1/3-octave bandwidths. One advantage is that this bandwidth at frequencies above 500 Hz corresponds well to the frequency selectivity of the human auditory system.

Dewesoft CPB solution supports up to 1/24-octave bandwidth.

What are frequency weighting curves?

A human ear doesn't have an equal "gain" at different frequencies. We will perceive the same level of sound pressure at 1 kHz louder than at 100 Hz. To compensate for this "error", we use frequency weighting curves, which give the same response as the human ear has.

The most commonly known example is frequency weighting in sound level measurement where a specific set of weighting curves known as A, B, C, and D weighting as defined in the IEC 61672 standard.

Unweighed measurements of sound pressure do not correspond to perceived loudness because the human ear is less sensitive at too low and high frequencies. The curves are applied to the measured sound level, by the use of a weighting filter in a sound level meter.

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