microphone headphone digital filters audio engineer DSP noise

Many Audio/acoustics engineers and researchers and audio hobbyists work with DSP (Digital Signal Processing). Some now and then, some on daily basis. Working on DSP for audio and speech, common challenges to create digital filters are: Noise cancellation, due to interference and Audio and Speech enhancement. And for whom DSP is not his daily job: filter design in general. In this blog, you’ll find out how the ASN Filter Designer may help for both experienced audio engineers and engineers where DSP is not their daily job to create digital filters for audio and speech.

For whom? For those with some and experienced DSP knowledge alike

If you are a audio/acoustics engineer or researcher or hobbyist: ASN Filter Designer is tailored for whom DSP is not his daily job and with some knowledge DSP. For those who need filter design and have to create some signal analysis. But also for those whom DSP is his daily job and want to save time and money. Most engineers who are working with DSP on a daily basis, are usually working with extensive but also expensive tools. Or want to do the maths themselves. Also for them ASN Filter Designer is useful:

  • Intuitive and easy to use.
  • Save days of time spending calculating on your own for the price of 2-3 hours of work.
  • Few lesser costs then extensive tooling with features you don’t use anyway.
  • Automatic code generation: export for further analysis to Matlab, etc, or to Cortex-M Arm based processors via the Arm CMSIS-DSP software framework.

How DSP for Speech and audio benefit from ASN Filter Designer:

  • Experiment with a variety of equalisation, noise cancellation and sound effect audio filtering algorithms.
  • Perform data analysis in the frequency domain and via specialised methods, including Cepstral analysis on the streaming data.
  • Import your own wav audio files (mono or stereo up to 48kHz) for streaming, and modify the filter characteristics in real-time while listening to the filtered audio stream.

Some features for creating digital filters for Audio and Speech:

The sampling frequency may be specified up to 4 decimal places

Sampling frequency

which is useful for designing filters based on fractional sampling frequencies, such as multiples of the 44.1kHz audio standard. Common examples include audio interpolation filters: 44.1kHz × 128 = 5.6448MHz and 44.1kHz × 256 = 11.2896MHz.

Filter orders of up to 499

may be constructed, where this is limited to 200 for streaming audio applications. As with the IIR filters, a FIR’s zeros may be modified by the P-Z editor (Method dropdown list changes to User defined), including the ability of adding poles and converting it into an IIR filter.

Audio and user data playback streaming

Signal Generator Controller: 
Choose what you want to listen to; Adjust the amplitude of the input signal
Signal Generator Controller:
Choose what you want to listen to; Adjust the amplitude of the input signal

The signal analyzer allows designers to test their design on audio, real (user) data or synthetic data via the built-in signal generator. Default data playback is implemented as streaming data, providing a simple way of assessing the filter’s dynamic performance, which is especially useful for fixed point implementations. Both frequency domain and time domain charts are fully supported, allowing for design verification via transfer function estimation using the cross and power spectral density functions. As with all other charts, the signal analyzer chart fully supports advanced zooming and panning, as well as comprehensive chart data file export options.

Load .wav for playback

The signal generator allows you to load .wav audio files for playback via the Audio File method. Both mono and stereo formats are fully supported for 8.000, 11.025, 16.000, 22.05, 44.1 and 48kHz. sampling rates. There is no restriction as to the length of the .wav file.

You may add extra signals to input audio stream

Use the signal generator to add sinewaves and white noise to the data stream.

Intuitive data analysis with the mouse

Move the mouse over the chart will automatically produce data markers and data analytics (shown at the bottom right side of the GUI). The signal analyzer is directly coupled to the filter designer GUI. This means that you may modify the filter characteristics, and see the effects in real-time in the signal analyzer. This functionality is very useful when designing audio filters, as the new filter settings can be heard immediately on the streaming audio feed.

Digital filters commonly used in audio and speech

speech and audio engineer researcher working on DSP digital filters microphone headphone

The ASN Filter designer includes digital filters commonly used in audio such as:

Read review here:

Top marks from Jacob Beningo

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