You are here: NI Home > Support > Product Reference > Manuals > Sound and Vibration Measurement Suite 6.0 Help

Performs common audio quality measurements when a pure tone is the expected signal. All measurements except DC and AC level are restricted to the specified frequency range. You also can remove DC signals from all measurements regardless of the specified frequency range. Distortion measurements allow you to quantify the linearity of the audio channel based only on the input signal and include THD and harmonics, THD+N, and SINAD. Channel evaluation measurements allow you to quantify the linear range of the audio channel based on the full-scale level and include gain, dynamic range, spurious-free dynamic range, noise level, and signal-to-noise ratio.

Dialog Box Options

Block Diagram Inputs

Block Diagram Outputs

Dialog Box Options

Parameter	Description
View	Specifies the display that appears in the Signals graph.
Signals	Displays the input signals, AC signals, or spectra. Use the Zoom button to zoom in and out of the display. Select the display you want to view from the View pull-down menu.
Autoscale	Automatically adjusts the scales of the graph to display the data.
Single-Tone Measurements	Displays the selected single-tone measurements in a table. Right-click the table to specify units for each measurement. You can replace the Signals graph with a larger Single-Tone Measurements table by selecting Results Table from the View pull-down menu. You can transpose the column and row information by clicking the Transpose button in the bottom right corner of the Single-Tone Measurements table. Transpose—Transposes the column and row information in the results table.
Input/Output	Contains the following options: Input signal—Configures the measurement for a single channel or N channels. Changing this selection changes the data types of the input signals and computed measurements. Export signals—Contains the following option: Export spectra—Exports the resulting spectra.
FFT Configuration	Specifies the FFT configuration. Window—Specifies the window to apply to the input signal. Contains the following options: None Hanning (default) Hamming Blackman-Harris Exact Blackman Blackman Flat Top 4 Term B-Harris 7 Term B-Harris Low Sidelobe Scaling—Specifies the scaling parameters. Spectrum type—Specifies whether the converted spectrum has units of magnitude or power (magnitude^2). Peak conversion—Specifies the peak scaling of the converted spectrum. You can select RMS (default), Peak, or Peak to Peak. Magnitude scale—Specifies whether the converted spectrum is expressed in a linear scale or in decibels.
Single-Tone Measurements	Specifies single-tone measurement options. Distortion—You can right-click any of the following options to launch the Specify Measurement Units dialog box to change or confirm the unit for each measurement. Contains the following options: SNR—Performs a signal-to-noise ratio (SNR) analysis and returns the SNR without harmonics. SINAD—Performs a signal in noise and distortion (SINAD) analysis. Total harmonic distortion plus noise (THD + N) is the negative of SINAD in dB. THD+N—Performs a total harmonic distortion plus noise (THD+N) analysis. Signal in noise and distortion (SINAD) is the negative of THD+N in dB. THD—Performs a harmonic analysis, including measuring the fundamental tone and harmonics, and returns the total harmonic distortion (THD). Harmonics—Performs a harmonic analysis, including measuring the fundamental tone and harmonics, and returns the harmonic components up to the specified Maximum harmonic. Channel Evaluation—Specifies channel evaluation options. Gain—Computes the gain based on the identified fundamental tone in the input signal and the Full-scale amplitude (EU pk). Dynamic range—Computes the dynamic range based on the input signal and the Full-scale amplitude (EU pk). SFDR—Computes the spurious-free dynamic range (SFDR) based on the input signal. Band power—Computes the total energy in the Input signal within the specified Measurement Range. Noise level—Computes the median noise level. The median noise level is an accurate estimate of the noise, even in the presence of a dominant fundamental tone and harmonics. Remove DC—Specifies whether to remove the DC component from the input signal before computing the single-tone measurements. Full-scale amplitude (EU pk)—Specifies the full-scale amplitude of a pure tone applied to the input of the device under test. Maximum harmonic—Specifies the highest harmonic number for total harmonic distortion (THD) computations. For example, if maximum harmonic is 3, harmonics 2 and 3 are the only harmonics used to compute THD. The default is –1. All—Specifies that all harmonics present in the input signal in the Measurement Range are measured. Measurement Range—Defines the bandwidth for all tone identification and noise measurements. Contains the following options: Start frequency (Hz)—Specifies the start frequency of the measurement. This option is coerced to the nearest spectral bin. The default is 20. You also can use the vertical, green cursors on the Spectra graph to change the value of Start frequency (Hz) and Stop frequency (Hz). Stop frequency (Hz)—Specifies the stop frequency of the measurement. This option is coerced to the nearest spectral bin. The default is 20k. You also can use the vertical, green cursors on the Spectra graph to change the value of Start frequency (Hz) and Stop frequency (Hz).

Block Diagram Inputs

Parameter	Description
input signal	Specifies the input signal for the measurement.
error in	Describes error conditions that occur before this Express VI runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.

Block Diagram Outputs

Parameter	Description
spectrum	Returns the computed spectrum. This input appears only if you place a checkmark in the Export spectra checkbox.
spectrum info	Returns information about the spectrum needed by the Spectrum Extended Measurements VIs and the Waterfall Display VIs. Do not modify the spectrum info values. This output appears only if you place a checkmark in the Export spectra checkbox.
fundamental tone	Returns the fundamental tone of the measurement. frequency—Returns the frequency of the detected fundamental tone in hertz. amplitude—Returns the amplitude of the detected fundamental tone.
harmonics	Returns the measured frequencies and amplitudes of the harmonics of the fundamental tone. frequency [Hz]—Returns the measured frequency, in hertz, of an individual harmonic component. amplitude—Returns the measured amplitude of an individual harmonic component.
distortion	Returns the results of the distortion measurements. SNR—Returns the measured signal to noise ratio (SNR) defined as the ratio of the root-mean-square (RMS) energy of the fundamental tone to the RMS energy of the noise. SINAD—Returns the measured signal in noise and distortion (SINAD), which is defined as the ratio of the RMS energy of the input signal to the RMS energy of the input signal less the RMS energy of the fundamental tone. THD+N—Returns the measured total harmonic distortion plus noise (THD+N), which is defined as the ratio of the RMS energy of the input signal less the RMS energy of the fundamental tone to the RMS energy of the input signal. THD—Returns the measured total harmonic distortion (THD), which is defined as the ratio of the RMS energy of the harmonics to the RMS energy of the fundamental tone.
channel evaluation	Returns the results of the channel evaluation measurements. gain—Returns the ratio of the measured amplitude of the input signal to Full-scale amplitude (EU pk). dynamic range—Returns the ratio of the highest signal level the device under test can handle to the lowest signal level it can handle. SFDR—Returns the dynamic range over which the input signal is free from spurious, or unwanted, sinusoidal components. band power—Returns the measured total power in the specified measurement range. median noise level—Returns the noise level of the input signal in the specified frequency range. The median noise level is a measure of the noise floor as computed from the power spectral density (PSD) and provides an accurate measure of the noise floor, even in the presence of a dominant fundamental tone and harmonics.
error out	Contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.
unit label	Returns the unit label for the input signal.