What's wrong with ringing?
 

I often see texts that imply or state outright that ringing in time-domain
audio waveforms, usually associated with time-domain discontinuities,
is to be avoided. I wonder what is the basis for this.

For example, if you take a perfect square wave with all of its harmonics,
and mathematically remove all of those above a certain point you will
see a waveform with ringing. I think this is referred to as Gibbs'
Phenomenon.

However far from being a problem, assuming you do have to
band-limit a signal, the presence of ringing (in this case, anyway)
seems to show:

- perfect removal of all frequencies above a certain point; and

- perfectly preserved amplitude and phase relationships amongst the
remaining frequency components.

As long as a filter perserves all human-audible frequencies I cannot see
an objection (to this form of ringing, at least). The only argument
I can think of for objecting is the possibility that the non-linear
behaviour of the ear may result in specific audibility issues which
wouldn't be heard with fully linear hearing. Indeed, I do see
articles that cast doubt on the audibility of ringing. For example
http://www.stereophile.com/reference/106ringing/.

So is ringing a bad thing per se? Or are there specific forms that
cause problems?

--
John Phillips

What's wrong with ringing?
 

In article , John Phillips
wrote:
I often see texts that imply or state outright that ringing in
time-domain audio waveforms, usually associated with time-domain
discontinuities, is to be avoided. I wonder what is the basis for this.

The argument seems to be primarily about 'pre' ringing. See below.

For example, if you take a perfect square wave with all of its
harmonics, and mathematically remove all of those above a certain point
you will see a waveform with ringing. I think this is referred to as
Gibbs' Phenomenon.

The distinction I think people have latched onto is that if you use one of
the familiar types of analogue LP filter, then any ringing tends to occur
after the transitions of the square-wave. This tends to be interpreted as a
'causal' requirement. That the filter can't react to the transition until
it occurs. Although this interpretation is rather shakey since it is quite
possible for the entire pattern to have been delayed in transit though the
filter, so any 'pre' transition ringing may be entirely causal - even with
an analogue system.

However far from being a problem, assuming you do have to band-limit a
signal, the presence of ringing (in this case, anyway) seems to show:

- perfect removal of all frequencies above a certain point; and

- perfectly preserved amplitude and phase relationships amongst the
remaining frequency components.

Well, ringing visible on something like a scope can be removed if you allow
the slope/shape of the LP filter to be fairly gradual. See, for example,
the work by Peter Craven in JAES. The results can remain time symmetric,
but the cost is a fairly gentle filter that then either cuts the HF inband
and/or passes rubbish out of band.

I note though that Meridian have now used a filter that gets all the
ringing post transitions. Suspect this was based on Peter Craven's work.
The downside it a tendency to phase spread, I assume.

As long as a filter perserves all human-audible frequencies I cannot see
an objection (to this form of ringing, at least). The only argument I
can think of for objecting is the possibility that the non-linear
behaviour of the ear may result in specific audibility issues which
wouldn't be heard with fully linear hearing. Indeed, I do see articles
that cast doubt on the audibility of ringing. For example
http://www.stereophile.com/reference/106ringing/.

See also the articles on this on audiomisc in the 'hearing' section which
also considers hearing nonlinearity in this context.

FWIW I am less than convinced ringing is audible in time symmetric filters.
It seems to be another of the popular ideas in audio for which I've not
personally found any reliable evidence. But given hearing nonlinearities,
it might be audible. So I would not totally dismiss the idea from what I
know at present.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

What's wrong with ringing?
 

"John Phillips"

I often see texts that imply or state outright that ringing in time-domain
audio waveforms, usually associated with time-domain discontinuities,
is to be avoided. I wonder what is the basis for this.


** So you have no idea that overshoot and ringing on a square wave trace is
generally synonymous with a HF peak in the response curve ? That is why
folk get so anxious and all worked up about it.

Even when you produce a response curve and show there is minimal or simply
no peak there in the case of sharp roll off HP filter, it is impossible to
convince all the neurotic, anxiety ridden, eye believing, ear disbelieving,
dim witted, pedantic rote learners they are wrong.

The world of hi-fi audio is chock full of ******s - not experts.

BTW:

the listening test described in that Stereophile article ( drivel really) is
highly flawed.



...... Phil

What's wrong with ringing?
 

"Phil Allison"

Correction:

** So you have no idea that overshoot and ringing on a square wave trace
is
generally synonymous with a HF peak in the response curve ? That is why
folk get so anxious and all worked up about it.

Even when you produce a response curve and show there is minimal or simply
no peak there in the case of sharp roll off LP filter, it is impossible to
convince all the neurotic, anxiety ridden, eye believing, ear disbelieving,
dim witted, pedantic rote learners they are wrong.

The world of hi-fi audio is chock full of ******s - not experts.

BTW:

the listening test described in that Stereophile article ( drivel really)
is
highly flawed.



..... Phil

What's wrong with ringing?
 

"John Phillips" wrote
in message

I often see texts that imply or state outright that
ringing in time-domain audio waveforms, usually
associated with time-domain discontinuities,
is to be avoided. I wonder what is the basis for this.

These texts seem to be promulgating a misapprehension. The misapprehension
seems to be that all reproduced square waves with ripples in or around them,
have those ripples because of ringing. Just because a reproduced square wave
has ripples in or around it, is not evidence of ringing.

Ringing is a very specific thing - it is a resonance. It is what a good bell
does - it resonates. It is true that if you reproduce a square wave through
a resonant circuit, there will be ripples in the reproduced signal. The
fallacy is the false idea that all reproduced square waves with ripples in
or around them are due to ringing.

For example, if you take a perfect square wave with all
of its harmonics, and mathematically remove all of those
above a certain point you will see a waveform with
ringing. I think this is referred to as Gibbs'
Phenomenon.

Actually, there is no ringing. There are no rising variations from flat
frequency response. There is nothing added or accentuated in the reproduced
signal.

However far from being a problem, assuming you do have to
band-limit a signal, the presence of ringing (in this
case, anyway) seems to show:

- perfect removal of all frequencies above a certain
point; and

- perfectly preserved amplitude and phase relationships
amongst the remaining frequency components.

Agreed. The actual problem is one of a poor word choice - we call those
ripples ringing because they resemble a different situation that is properly
called ringing.

As long as a filter preserves all human-audible
frequencies I cannot see an objection (to this form of
ringing, at least).

Agreed.

The only argument
I can think of for objecting is the possibility that the
non-linear behaviour of the ear may result in specific
audibility issues which wouldn't be heard with fully
linear hearing.

Just because someone hypothesizes such a problem, does not mean that it
exists. Reliable evidence in this area would come from a properly-done
listening test. In fact properly-done listening tests don't confirm the
hypothesis that this problem exists.

Indeed, I do see
articles that cast doubt on the audibility of ringing.
For example http://www.stereophile.com/reference/106ringing/.

The article presents some apparently correct facts, but then fails to reach
a reasonable conclusion because it perpetuates an audiophile myth:

"But even in the earliest days of domestic digital audio there were
dissenting voices. Many hi-fi writers, myself included, were thoroughly
underwhelmed by our initial experiences of Compact Disc, and so were some
influential audio professionals, such as Doug Sax."

Doug Sax was an expert and influential vinyl mastering engineer. He has an
obvious source of prejudice and bias in his life. The practical death of the
LP as a dominant form of media severely reduced the need for skills that he
had devoted much of his life to. This is not a technical problem, it is a
life's strategy problem. It is not a music industry problem, it is a
career-choice problem for one man.

"Over a period of some years the intensity of this opposition to CD
decreased somewhat, but many commentators and ordinary audio consumers
concluded that there was something fundamentally amiss with 16/44.1 and
16/48 audio. Many of them voted with their feet, continuing to prefer the
sound of the "obsolescent" LP."

This is an almost completely false statement. By 2006 when he article was
written, nearly 99% of the market for LPs had disappeared. Where once nearly
100% of all music lovers bought LPs, now nearly 100% of all music lovers
bought music in some other music delivery format.

In fact the overwhelming majority of commentators and ordinary audio
consumers had abandoned the LP by 2006. Outside of the bizarre world of
high end audio, and the very serious but tiny and shrinking world of
collectors of legacy recordings, nobody much cared much about the LP format
at all. The subsequent commercial failure of the SACD and DVD-A formats
underscored how little people cared about these alleged problems.

So is ringing a bad thing per se? Or are there specific
forms that cause problems?

What's wrong with ringing?
 

John Phillips wrote:

I often see texts that imply or state outright that ringing in time-domain
audio waveforms, usually associated with time-domain discontinuities,
is to be avoided. I wonder what is the basis for this.

Ringing on square wave inputs may be a sign of maginal stability.

Graham

What's wrong with ringing?
 

On 2008-07-07, Jim Lesurf wrote:
In article , John Phillips
wrote:
For example, if you take a perfect square wave with all of its
harmonics, and mathematically remove all of those above a certain point
you will see a waveform with ringing. I think this is referred to as
Gibbs' Phenomenon.

The distinction I think people have latched onto is that if you use one of
the familiar types of analogue LP filter, then any ringing tends to occur
after the transitions of the square-wave. This tends to be interpreted as a
'causal' requirement. That the filter can't react to the transition until
it occurs. Although this interpretation is rather shakey since it is quite
possible for the entire pattern to have been delayed in transit though the
filter, so any 'pre' transition ringing may be entirely causal - even with
an analogue system.

This is one of the issues I see. Nothing is, in practice, acausal.

The fact that in the square wave Gibbs Phenomenon example something
appears to happen before the transition is nothing at all to do
with acausality. There are differences in time-domain behaviour
between difital and analogue filters but I ask myself whether applying
"conventional wisdom" learned from the analogue case to the digital case
is rather flawed.

... snip ...
I note though that Meridian have now used a filter that gets all the
ringing post transitions. Suspect this was based on Peter Craven's work.
The downside it a tendency to phase spread, I assume.

Yes. I saw that from Meridian and asked myself if it was marketing
or engineering.

... snip ...
See also the articles on this on audiomisc in the 'hearing' section which
also considers hearing nonlinearity in this context.

OK I will look.

FWIW I am less than convinced ringing is audible in time symmetric filters.
It seems to be another of the popular ideas in audio for which I've not
personally found any reliable evidence. But given hearing nonlinearities,
it might be audible. So I would not totally dismiss the idea from what I
know at present.

Agreed.

--
John Phillips

What's wrong with ringing?
 

On 2008-07-08, Arny Krueger wrote:
"John Phillips" wrote
in message

I often see texts that imply or state outright that
ringing in time-domain audio waveforms, usually
associated with time-domain discontinuities,
is to be avoided. I wonder what is the basis for this.

These texts seem to be promulgating a misapprehension. The misapprehension
seems to be that all reproduced square waves with ripples in or around them,
have those ripples because of ringing. Just because a reproduced square wave
has ripples in or around it, is not evidence of ringing.

Ringing is a very specific thing - it is a resonance. It is what a good bell
does - it resonates. It is true that if you reproduce a square wave through
a resonant circuit, there will be ripples in the reproduced signal. The
fallacy is the false idea that all reproduced square waves with ripples in
or around them are due to ringing.

Exactly. Someone has applied the "conventional wisdom" of the analogue
world in an inappropriate way to the digital world. The word "ringing"
seems now to be overloaded with incompatible meanings. It is actually
used nowadays to describe an observed phenomenon, but an incorrect
inference seems then to be drawn about a cause called "ringing" which
isn't clearly present.

--
John Phillips

What's wrong with ringing?
 

In article , Eeyore
wrote:


John Phillips wrote:

I often see texts that imply or state outright that ringing in
time-domain audio waveforms, usually associated with time-domain
discontinuities, is to be avoided. I wonder what is the basis for
this.

Ringing on square wave inputs may be a sign of maginal stability.

Key phrase here is "may be". I recall reading in the past more than one
review of a power amp where the writer assumed that 'ringing' on a square
wave was a sign of marginal stability. Whereas in many cases it simply
showed that the amp included a series inductor on its output to ensure safe
and stable operation into naster RF loads. Another example where it was
possible for writers to jump to conclusions based upon limited
understanding.

My impression is that it has been common for digital filtering in domestic
items like CD players to use FIR arrangements. Stability should not be a
problem for these. But may be more of an issue for IIR designs. Indeed, if
I recall correctly, some of the high order delta-sigma modulator (i.e. ADC)
arrangements published by Sony and Philips for DSD/SACD had potential
instability unless used correctly.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

What's wrong with ringing?
 

"Arny Krueger"

These texts seem to be promulgating a misapprehension. The misapprehension
seems to be that all reproduced square waves with ripples in or around
them, have those ripples because of ringing. Just because a reproduced
square wave has ripples in or around it, is not evidence of ringing.


** The term "ripples" refers to cyclic variations in the gain of a ( LP)
filter in the pass or stop bands.

Various classes of filter have either none, one or the other or both.

Wiki has some good info on this.


Ringing is a very specific thing - it is a resonance.


** Not true.

The term " ringing " has more than one meaning in electronics.

It mostly refers to any visible overshoot and oscillation pattern with a
step input to a circuit - whether or not related to an actual peak in the
pass band gain.



...... Phil