DIY Audio Analyser

[Oberlix]

Hi all diyaudio readers,

I am third year Audio Technology student and the time has now come for me to do my third year project. I am aiming towards building an arduino based audio analyser if it is possible, however before I go any further I need to establish the market / need for my project in the real world.

So I ask you all for your help and literally 5 minutes of your time, if you could do this survey it would be much appreciated.

DIY Audio Analyser Survey

also I would be very interested in your opinions and ideas in general on the subject of audio analysers.

Thank you for your time
Oberlix

[counter culture]

I've used many dedicated test sets for radio.

A DIY audio analyser would be nice.

An entry-level new audio analyser costs ~$5000.

In order to be worthwhile an analyser must be accurate and have a good resolution, and that means it must perform better than the DUT.

You can see the kind of performance required by looking at dScope and Audio Precision test sets.

It's possible, likely even, that the level of performance required is beyond that of a 3rd. year graduate student project. Since one of the things likely to come under test is a soundcard, performance should exceed that of a quality soundcard. Google 'audio widget'.

Some things missing from your list of tests are noise, IMD, crosstalk and jitter.

I'm not quite sure how an arduino will fit in, unless it's just providing a USB interface. My preference would be a PIC (google 'Building_a_PIC18F_USB_device') You almost certainly want to use a PC for its display capabilities. Organising a real-time display may require careful use of the USB bandwidth, and you will need some Windows or Linux GUI development skills, Visual Basic as a minimum.

Just getting a few measurements calibrated, up and running and showing an appreciation of the resolution required in a useful instrument would probably constitute sufficient to get a high mark for your project.

Good luck.

[teachjava]

Originally Posted by Oberlix

Hi all diyaudio readers,

I am third year Audio Technology student and the time has now come for me to do my third year project. I am aiming towards building an arduino based audio analyser if it is possible, however before I go any further I need to establish the market / need for my project in the real world.

So I ask you all for your help and literally 5 minutes of your time, if you could do this survey it would be much appreciated.

DIY Audio Analyser Survey

also I would be very interested in your opinions and ideas in general on the subject of audio analysers.

Thank you for your time
Oberlix

Where do you go to school for audio?

[Oberlix]

Hi teachjava,

I'm studying at Southampton Solent University.

Oberlix

[Oberlix]

Counter Culture,

Thank you for your feedback, your perfectly write about the capabilities required and I will be aiming to get as accurate as possible within the time limit of my project. In terms of satisfying my degree criterion for the project module if I get an fft or Goertzel algorithm properly working I will of achieved this.

I'm intrigued with your preference for the pic 18, why would you side with these devices?

Thank you for your time
Oberlix

[counter culture]

Why PIC?

I prefer to work directly with a chip, rather than a board. It's more flexible, and I happen to know that there's a working USB implementation available for download.

The arduino is promoted as a system for artists, designers, hobbyists. I don't have direct experience of it, but the experience I do have of systems intended to 'simplify' development is that what you learn about using them is not necessarily portable. Of course there are features of the PIC that mean that if you learn to program them in assembly language then you will have to learn a new vocabulary if you change to say, Atmega processors, but more of the experience will carry over.

Another problem with 'accessible' systems is that they often omit to provide access to all the capabilities of a chip. Even where this is not the case, facilities may be implemented in nonstandard ways which are of limited value in a professional environment.

There are other reasons which will not apply to you.

At home, I have a PicKit2 in-system USB programmer for PICs (which BTW is cheap).

I have an existing codebase for the PIC in assembler and C. This means that in most instances I don't start to write a program from scratch, I take a bit of working code and modify it.

I would still recommend that you learn to program in assembly language and C. C provides a level of abstraction with a minimal compromise of performance. Most C compilers allow the embedding of inline assembly language where maximum performance is required. Most compilers also produce assembly language as an intermediate step to machine code, and if inline assembler is not supported the intermediate files can be hacked. Assembly language provides the maximum performance and uncompromised access to the features of the hardware.

Of course there are advantages to systems such as the arduino. The learning curve is not as steep. Many of the features commonly required such as USB ports are already implemented in firmware, which can be a big time-saver. I don't implement floating point maths in assembly language, I use a C library.

There's no hard-and-fast right and wrong, it's a judgement call as to which route you choose.

[ThorstenL]

Hi,

Originally Posted by Oberlix

I am third year Audio Technology student and the time has now come for me to do my third year project. I am aiming towards building an arduino based audio analyser if it is possible, however before I go any further I need to establish the market / need for my project in the real world.

Suggested features:

1) PC/Mac connected "external USB sound card" for use with analysis software (RMAA etc).

2) Ideally powered fully from USB Bus with an option for quiet, linear external PSU.

3) Minimum 24/96KHz sample rate (192KHz preferred).

4) AD and DA with > 120dB DNR.

5) Analog stages build with measurements in mind, including calibration options, protection, BNC Connectors on Board etc.

6) Includes single channel Microphone preamp, Phantom Power Supply for Behringer ECM8000 Microphone and a single channel 1W amplifier to allow easy stand alone measurements of speakers from Battery powered laptop outdoors.

Ciao T

[abraxalito]

Originally Posted by Oberlix

Thank you for your feedback, your perfectly write about the capabilities required and I will be aiming to get as accurate as possible within the time limit of my project. In terms of satisfying my degree criterion for the project module if I get an fft or Goertzel algorithm properly working I will of achieved this.

A DIY analyser has a different set of requirements from an AP or dScope. Those machines are doing double duty (at least) - they're used for both R&D and production test. The DIY analyser dispenses with the production test aspects and hence doesn't really need the level of accuracy those boys provide.

The Goertzel algorithm is a good one to use to find, e.g. how much 2nd/3rd/5th harmonic distortion a device is generating as FFT does lots of calculations for frequencies where no signal is expected to lie. The big disadvantage of FFT is the fact that its not real-time in most analysers. For DIY use I feel real-time feedback is much more useful and as an end customer I'd willingly trade this off for overall accuracy. Who really cares if the THD figure is accurate to 1% or 10%?

Just my 2p-worth

[SY]

If this includes an external box, a BNC input with 1M impedance would be great (this is what I built into my own interface box). That way, 10x scope probes can be used so as not to excessively load down high impedance circuits.

[hidnplayr]

Originally Posted by SY

If this includes an external box, a BNC input with 1M impedance would be great (this is what I built into my own interface box). That way, 10x scope probes can be used so as not to excessively load down high impedance circuits.

+1 on that