Testing filters?

[soundmodel]

What kind of practices exist for evaluating filter designs? E.g. stability, phase characteristics etc.?

How much in musical applications can be based on merely listening and what are things that are better analyzed using plotting or automated tests?

[Miles1981]

First, you need to explain what you mean by filter design. Filter is a general term that encompasses LTI systems, but also all the rest (dynamics, distortion...).
If you are referring to EQ (LTI systems), then yes, stability (and also are the roots close to the unit circle or not) and mainly spectrum content (amplitude and phase).
And I think nothing can be based on mere listeing. Everyone has a different ear, different setup...

[stratum]

If you are referring to EQ (LTI systems), then yes, stability (and also are the roots close to the unit circle or not) and mainly spectrum content (amplitude and phase).

How do you test for `stability` (if that`s the right word) in other senses? For example parameter modulation robustness?
I had asked a similar question here but couldn`t find a definite answer: http://www.kvraudio.com/forum/viewtopic ... 3&t=464791

There are many similar problems :

- Detect presence of aliasing and determine whether it is audible
- Detect D.C. accumulation and determine whether it has detrimental consequences in an algorithm
- Detect quantization noise caused by limited numerical precision and high sampling rates
- Detect whether a filter is unstable (in the above sense you mention) due to a numerical problem instead of a theoretical one
- Detect audibility of errors due to interpolation or spectral leakage ( as implied by the authors if `serum` here, apparently many couldn`t find these problems before releasing their products https://www.xferrecords.com/products/serum ) :

Playback of wavetables requires digital resampling to play different frequencies. Without considerable care and a whole lot of number crunching, this process will create audible artifacts. Artifacts mean that you are (perhaps unknowingly) crowding your mix with unwanted tones / frequencies. Many popular wavetable synthesizers are astonishingly bad at suppressing artifacts - even on a high-quality setting some create artifacts as high as -36 dB to -60 dB (level difference between fundamental on artifacts) which is well audible

In what sense -60dB is audible? That`s also a curious question in itself.