# Delta between two decibel signal
**URL:** https://discourse.processing.org/t/delta-between-two-decibel-signal/41442
**Category:** Coding Questions
**Created:** [March 25, 2023, 4:57pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442 "2023-03-25T16:57:01Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@bking](https://discourse.processing.org/u/bking)
#### Post date: [March 25, 2023, 4:57pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442/1 "2023-03-25T16:57:01Z")
Hi,
I’m trying to return the difference between to signal.
The difference is L1
I tried this but the problem is with pow
Thanks for helping 😉
```auto
float splitTimeLfo, oldSplitTimeLfo;
void setup() {
int i = 12;
println(log(i));
println(log10(i));
// float differenceSignal= splitTimeLfo + log10( 1 - 10 * pow (-(splitTimeLfo-oldSplitTimeLfo)/10));
print ( differenceSignal);
}
// Calculates the base-10 logarithm of a number
float log10 (float x) {
return (log(x) / log(10));
}
```
---
### Author:  [@mnse](https://discourse.processing.org/u/mnse)
#### Post date: [March 25, 2023, 5:28pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442/2 "2023-03-25T17:28:49Z")
Hi @bking,
What is the problem with pow ?
Just use 1-pow(10,…)
[https://processing.org/reference/pow\_.html](https://processing.org/reference/pow_.html)
Cheers
— mnse
---
### Author:  [@bking](https://discourse.processing.org/u/bking)
#### Post date: [March 25, 2023, 5:50pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442/3 "2023-03-25T17:50:15Z")
I tried this but not good
```auto
float splitTimeLfo = 5;
float oldSplitTimeLfo = 15;
void setup() {
int i = 12;
println(log(i));
println(log10(i));
// float differenceSignal= splitTimeLfo + log10( 1 - 10 * pow (-(splitTimeLfo-oldSplitTimeLfo)/10));
float differenceSignal= splitTimeLfo + log10( 1 - 10 -1-pow(10,-(splitTimeLfo-oldSplitTimeLfo)/10));
print ( differenceSignal);
}
// Calculates the base-10 logarithm of a number
float log10 (float x) {
return (log(x) / log(10));
}
```
---
### Author:  [@mnse](https://discourse.processing.org/u/mnse)
#### Post date: [March 25, 2023, 5:57pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442/4 "2023-03-25T17:57:56Z")
Try to use floating point notation for your numbers.
Means not 10, but 10.0 etc …
Cheers
— mnse
---
### Author:  [@bking](https://discourse.processing.org/u/bking)
#### Post date: [March 25, 2023, 6:27pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442/5 "2023-03-25T18:27:51Z")
i have infinity as result
```auto
float splitTimeLfo = 5;
float oldSplitTimeLfo = 15;
void setup() {
int i = 12;
println(log(i));
println(log10(i));
// float differenceSignal= splitTimeLfo + log10( 1 - 10 * pow (-(splitTimeLfo-oldSplitTimeLfo)/10));
float differenceSignal= splitTimeLfo + log10( 1.0 - 10.0 -pow(1-10.0,-(splitTimeLfo-oldSplitTimeLfo)/10.0));
print ( differenceSignal);
}
// Calculates the base-10 logarithm of a number
float log10 (float x) {
return (log(x) / log(10));
}
```
---
### Author:  [@bking](https://discourse.processing.org/u/bking)
#### Post date: [March 25, 2023, 6:29pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442/6 "2023-03-25T18:29:04Z")
I think it is ok now !
```auto
float splitTimeLfo = 5;
float oldSplitTimeLfo = 15;
void setup() {
int i = 12;
println(log(i));
println(log10(i));
// float differenceSignal= splitTimeLfo + log10( 1 - 10 * pow (-(splitTimeLfo-oldSplitTimeLfo)/10));
float differenceSignal= splitTimeLfo + log10( 1.0 - 10.0 *pow(1-10.0,-(splitTimeLfo-oldSplitTimeLfo)/10.0));
print ( differenceSignal);
}
// Calculates the base-10 logarithm of a number
float log10 (float x) {
return (log(x) / log(10));
}
```
Thank u very much!
---
### Author:  [@bking](https://discourse.processing.org/u/bking)
#### Post date: [March 25, 2023, 6:34pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442/7 "2023-03-25T18:34:42Z")
it works but not always.
Maybe the difference between two signals have to respect a rule?
```auto
float splitTimeLfo = 6;
float oldSplitTimeLfo = 5;
void setup() {
int i = 12;
// println(log(i));
// println(log10(i));
// float differenceSignal= splitTimeLfo + log10( 1 - 10 * pow (-(splitTimeLfo-oldSplitTimeLfo)/10));
float differenceSignal= splitTimeLfo + log10( 1.0 - 10.0 *pow(1-10.0,-(splitTimeLfo-oldSplitTimeLfo)/10.0));
print (" differenceSignal " + differenceSignal);
}
// Calculates the base-10 logarithm of a number
float log10 (float x) {
return (log(x) / log(10));
}
```
---
### Author:  [@quark](https://discourse.processing.org/u/quark)
#### Post date: [March 26, 2023, 3:17pm UTC](https://discourse.processing.org/t/delta-between-two-decibel-signal/41442/8 "2023-03-26T15:17:29Z")
> [@bking](#):
>
> Maybe the difference between two signals have to respect a rule?
The problem is that the log\_{10} of a number \le0 is undefined. This means that the following must be true for a meaningful result
1 - 10^\left({-(L-L\_2)\over10}\right) \> 0
Rearrange the formula and we get
10^\left({-(L-L\_2)\over10}\right) \< 1
Now take the log\_{10} of both sides are we get
\left({-(L-L\_2)\over10}\right) \< 0
multilply both sides by 10 and simplify the LHS we get
-L + L\_2 \< 0
Again after rearrangement
L \> L\_2
So (L \> L\_2) _ **must be true** _ for a meaningful result. 😄