Need for Audio features probe JSON fields explanation

206 views
Skip to first unread message

Sébastien Vitard

unread,
May 21, 2013, 8:15:20 AM5/21/13
to funf-de...@googlegroups.com
Hi,

I'm trying to play with the Audio features probe but I don't understand what data are returned in JSON:

"{
""diffSecs"":1.0789999961853027,
""l1Norm"":32.25625,
""l2Norm"":52.28364227939748,
""linfNorm"":22.93468988235943,
""mfccs"":
[
79.26603614546039,
6.74008322111781,
1.3429836887293989,
1.6715114584666757,
3.913417320441085,
3.4400956270685072,
1.6356878915289599,
2.7935779038080404,
2.2162465586243854,
0.12430272756951331,
0.39314584015074067,
3.010446482271461
],
""psdAcrossFrequencyBands"":
[
20950344.040772464,
1336069.3463328325,
695116.1195042991,
194519.98152231556
],
""timestamp"":1369134621.992
}"

Indeed, Javadoc is not helpful since it's just an enumeration of JSON fields and the Built-in probes v3 section doesn't mention this probe...

Can you add a little description of these fields in the Built-in probes v3 section, add a Built-in probes section in v4 documentation, or at least, explain them here?

Thanks in advance.

Sébastien Vitard

Sébastien Vitard

unread,
May 21, 2013, 8:27:24 AM5/21/13
to funf-de...@googlegroups.com
Sorry, the link to the Javadoc wasn't on the right page...

adelich

unread,
May 23, 2013, 7:39:17 AM5/23/13
to funf-de...@googlegroups.com
Hi Sèbastien
Could you tell me, please, what are duration and period values in your audio features probe scan. I'm asking, because if i scan with duration of 1 second, then i have nothing recorded in DB. But duration=2sec is working.

Adel

вторник, 21 мая 2013 г., 14:27:24 UTC+2 пользователь Sébastien Vitard написал:

Sébastien Vitard

unread,
May 23, 2013, 7:57:36 AM5/23/13
to funf-de...@googlegroups.com
I'm using this probe for noise level measurement purpose.
So, I take 30s measurements to get the best estimation without drain the battery too much.

adelich

unread,
May 23, 2013, 8:43:37 AM5/23/13
to funf-de...@googlegroups.com
I'm capturing also for noise estimation, but for user's actions recognition purpose.
Doing that i, capture 1 second of Audio Features every 5 seconds.
This means that i set Duration=1s and Period=5s.
The problem is, that if i set duration only 1 sec, then i have not the probe values in DB.
For duration =2 sec it works.

четверг, 23 мая 2013 г., 13:57:36 UTC+2 пользователь Sébastien Vitard написал:

Sébastien Vitard

unread,
May 24, 2013, 11:13:57 AM5/24/13
to funf-de...@googlegroups.com
After some search on the Web, I got my answer!

To compute the sound level, we have to apply this formula: 10 * log10( l1Norm^2 ).


Le mardi 21 mai 2013 14:15:20 UTC+2, Sébastien Vitard a écrit :

Михаил Сысоев

unread,
Feb 16, 2016, 8:44:49 AM2/16/16
to Funf Developers, sebastie...@gmail.com
Hi, could you please provide a link, where you found this formula?

Thank you, Mike

sebastie...@gmail.com

unread,
Feb 16, 2016, 9:24:38 AM2/16/16
to Funf Developers, sebastie...@gmail.com
Hi Mike,

I do not have access to my work on Funf anymore because I leaved the company for which I had to use it 2 years ago.
But I have found a link which describes how to compute the sound level from a sample : http://digital.ni.com/public.nsf/allkb/FCE0EC0A6B193A028625722E006DE298.

I adapted the formula to the data provided by the probe and it appears that the calculation in the log is quiet similar to what the l1Norm field is (because a tick of the handleAudioStream method happens about every 1s, see class AudioFeaturesProbe). But you can be more precise if you take into account the diffSecs field.

And for your info, the L1 value is the level exceeded for 1% of the time, so it's the most accurate measure (see http://www.epd.gov.hk/epd/noise_education/web/ENG_EPD_HTML/m2/types_3.html).

Best regards.

Михаил Сысоев

unread,
Feb 17, 2016, 5:18:03 AM2/17/16
to Funf Developers, sebastie...@gmail.com
Hi Sebastien,

Thank you for your help, this is very useful information. Let's me ask you one more question.
So, you actually changed integral to the l1norm? This is not clear for me.

thank you
Best regards, Mike
Reply all
Reply to author
Forward
0 new messages