FIR Filter: Silence in between

"Himanshu Chauhan" <hs.chauhan@gmail.com> wrote in message 
news:1114972129.832781.198830@f14g2000cwb.googlegroups.com...
> Hi Fred!
>
> Frankly speaking I also don't want to put in my efforts in learning
> matlab.
> At least for the time being.
>
> After getting LP and HP filters to work I was thinking about a bass
> boost
> effect. Could you please, point out the problem with my approach? What
> I am doing is this :-
> I filter all base frequencies (till 200 Hz) using the low pass filter.
> Then
> I add this to the original signal. I figured out a little improvement
> in bass
> but it introduces some noise as well. If I choose to add the filtered
> signal
> to original signal twice or thrice, the output is horribly noisy!
>

I'm sure that someone else can answer better than I.  Perhaps a new 
post/thread?

Normally filtering then adding to the original isn't the way to do a boost I 
should think.  Simply filter with a boost where you want it - and that is 
all.  It's all a matter of scale.

By filtering and adding you get a couple of things that are undesirable. 
You get a differential delay unless you compensate for it.  You get phases 
that could add destructively.  And you could get saturation.

As far as noise goes, if the signal is already near the top of the dynamic 
range then adding could cause saturation - which isn't exactly the same 
thing but could be an issue.  The ideal process, I would imagine, would make 
best use of the dynamic range without adding noise or much saturation.

Fred 

In article <1114972129.832781.198830@f14g2000cwb.googlegroups.com>,
Himanshu Chauhan <hs.chauhan@gmail.com> wrote:
>After getting LP and HP filters to work I was thinking about a bass
>boost
...
>I filter all base frequencies (till 200 Hz) using the low pass filter.
>Then
>I add this to the original signal. I figured out a little improvement
>in bass
>but it introduces some noise as well. If I choose to add the filtered
>signal
>to original signal twice or thrice, the output is horribly noisy!

What is your number/data type?  What is it's range?  If an arithmetic
operation either overflows or saturates the range, what to you think
the result will sound like?

If you scale down the intermediate calculation values or the result so
that they don't clip or overflow, will the result still sound like a boost,
or will it sound like a cut instead?


IMHO. YMMV.
-- 
Ron Nicholson   rhn AT nicholson DOT com   http://www.nicholson.com/rhn/ 
#include <canonical.disclaimer>        // only my own opinions, etc.

My data type is float. I was able to get a noise less boost by
attentuating the intermediate result to bring them into the range. But
as the number of time of addition increases, the noise increases in
proporttion.

I feel its not just the right approach!

Regards
--Himanshu

Hi,

As you know the low pass filter induce a delay on the signal. So, if you 
  add the original signal and the filtered one, it will be a phase 
between them. Try to delay the original signal of the same delay as the 
filter.

Y.K

Ronald H. Nicholson Jr. a �crit :
> In article <1114972129.832781.198830@f14g2000cwb.googlegroups.com>,
> Himanshu Chauhan <hs.chauhan@gmail.com> wrote:
> 
>>After getting LP and HP filters to work I was thinking about a bass
>>boost
> 
> ...
> 
>>I filter all base frequencies (till 200 Hz) using the low pass filter.
>>Then
>>I add this to the original signal. I figured out a little improvement
>>in bass
>>but it introduces some noise as well. If I choose to add the filtered
>>signal
>>to original signal twice or thrice, the output is horribly noisy!
> 
> 
> What is your number/data type?  What is it's range?  If an arithmetic
> operation either overflows or saturates the range, what to you think
> the result will sound like?
> 
> If you scale down the intermediate calculation values or the result so
> that they don't clip or overflow, will the result still sound like a boost,
> or will it sound like a cut instead?
> 
> 
> IMHO. YMMV.