Audio Record/Playback Circuit

[The Master]

Ive done some testing using goldwave. I encoded the most important sample using 11.025KHz (the closest option to 12KHz). The quality sounds really bad. Its like being put through a low-pass filter. Would this test be representative of those chips and if so are there any that support a higher sample rate?

[keithdoxey]

Bandwidth is half the sampling frequency so your 11K sample will only have a top end frequency of around 5.5kHz

If you want CD quality then you need to sample at 44.1kHz.

Sampling at 32kHz will give you quality similar to FM radio.

[The Master]

Im not sure what you mean there. I havnt seen bandwidth mentioned anywhere. The datasheet for these chips gives the sampling frequency (max 12KHz) and the tests i did also used sample rate.

[Ioannis]

The bandwidth (what you will hear) is the half of the sample you will take.

So for telephone quality a sample rate of 6-8khz is going to give you 3-4KHz bandwidth. What you define as filtered audio.

It is the price you have to pay for the A/D conversion in respect with he memory needed.

Ioannis

[Jerson]

For what it is worth, most of these chips are solid state alternatives for the tape in telephone answering machines. So, the quality you should expect is on par with phone quality. There may be a few variants which allow you to choose your sample rate. The APR series from Aplus Taiwan is one of such chips. Using segmentation and playing fill-ins, you can build really long messages. Some examples would be the announcement systems on the train / bus.

[The Master]

Hmm, that doesnt sound too bad then. I guess the only way i will find out for sure is to actually order some and see how they sound. If it turns out that they arent suitable then i have another idea. I seem to remember FTDI making an mp3 player chip or circuit. I know thats probably overkill for a short sample but if i used that i could use it for the longer files aswell.

I will order some of the ISD chips first though and see how they turn out. Thanks.