100 Things #63: Measure Frequency and Distortion in Real Time

SoundCheck features a full suite of versatile powerful virtual instruments, including a dedicated frequency counter and distortion analyzer. The frequency counter is perfect for finding the dominant frequency in a signal path. The distortion analyzer includes many different distortion measurement options, and even allows the user to select which specific harmonics to analyze. As with all virtual instruments in SoundCheck, both instruments can be used within a sequence with a virtual instrument acquisition step. Both instruments also include a strip chart recorder, perfect for measuring DUT performance over a long period of time.

Measure Frequency and Distortion in Real Time

Learn more about the frequency counter and distortion analyzer virtual instruments

Read all about SoundCheck’s full virtual instrument suite including the distortion analyzer and frequency counter, plus all of the powerful and useful functionality.

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You may already know that SoundCheck includes virtual instruments for quick, on-the-fly measurements. But, did you know SoundCheck has both a Frequency Counter and a Distortion Analyzer virtual instrument?

The frequency counter determines the dominant frequency in a signal path, analyzing it in real time and displaying the primary frequency. This tool is useful for calibrating audiometers, or any device where a pure tone needs to be identified to a very high precision and accuracy.

The distortion analyzer continuously measures the distortion in a signal path. This virtual instrument offers many different distortion measurements, including individual harmonics, total harmonic distortion or THD, where you can select which harmonics to analyze just like in the Analysis step, THD+N, THD and THD+N residual level, and signal-to-noise distortion ratio, or SINAD. In fact, many of SoundCheck’s distortion measurement methods are available right here in the distortion analyzer. There are many different use cases for this analyzer, but one example might be to measure real time distortion characteristics. An example might be to increase the signal level to a DUT using the signal generator, and use the distortion analyzer to see at what level the distortion crosses a particular threshold, for example: 3% THD.

Both instruments allow for linear or continuous averaging and variable time weighting, and limits can be set with clear visual feedback. As with all our virtual instruments, values can be saved to the memory list to be recalled in following sequence steps. This enables you, for example, to trigger a measurement at a certain frequency determined by the frequency counter. And, just like all virtual instruments in SoundCheck, both the distortion analyzer and frequency counter can be used within a sequence using a virtual instruments step.

These tools’ capabilities can be further extended with the strip chart recorder. This addition enables changes in frequency and distortion characteristics to be easily tracked over extended testing periods. For example, using the strip chart recorder with the distortion analyzer allows any changes in distortion percentage to be monitored over hours or even days. Similarly, the frequency counter can be used with the strip chart recorder to test the stability of a Bluetooth device over a time period to identify any problems with jitter or signal dropouts.

What virtual instrument would you like to see in SoundCheck? Let us know in the comments below. For more information on all things SoundCheck, be sure to head to Listen Inc . com.

Hearing Aid Frequency Response Test Sequence

This sequence follows the ANSI S3.22-1996 standard method for testing the frequency response of a hearing aid. An equalized stepped sine sweep from 8 kHz – 200 Hz is played at a level of 60 dBSPL through the anechoic box speaker, and the output of the hearing aid is analyzed with the Heterodyne algorithm to produce a frequency response. Next, the HFA (High Frequency Average) is calculated by averaging the response values at three frequencies (1000, 1600, 2500 Hz). The HFA is then subtracted by 20 dB. Two post processing steps are used to find the upper and lower frequency points at which the response curve intersects this calculated value (HFA – 20 dB). These are the high and low frequency cutoff points.