Travel Technology - Cell phone sound quality observations

Without naming the device, I have a GSM/WCDMA 850/900/1800/1900/2100 phone.

I am a sort of an audiophile, and appreciates 'good sound' . Can someone explain my observation, why

- GSM in Europe/Asia sounds wonderful? (especially the 900 band). GSM (with AT&T) in NYC, in contrast sounds downright awful.

- W/CDMA in Japan/South Korea also sounds great, but WCDMA in Europe does not sound so good, neither does it in the US.

Also, from my observation, NYC probably has the worst in terms of sound quality, it's much better in remote areas with a strong signal

Network settings (Audio codecs, phone codecs, RF signal)

GSM uses half and full rate, and also enhanced full codec.

This alters the sample rate of the audio, between 8k and about 22k if I remember correctly.

This means, depending on operator settings, network capacity, you can have varying quality. In general the denser the area, the lower the bit rate to increase capacity.

Now, in addition to the audio settings on the network, there are a large number of handset specific algorithms - echo canceller, equalisation, active noise suppression, dynamic level control etc

So, you have a wide variety of active network settings, and handset side algorithms that fluctuate quality DEPENDING on the network settings.

Then there are other factors, for example the RF signal strength. A lower signal strength may force higher bit error rates (BER) which manifest themselves in broken and poorer audio. Data is getting lost in the connection, and typically the audio suffers.

Finally, there is the environment. Louder background noise will increase the activity of certain algorithms, mainly noise/background noise suppressors, in addition to making the phones voice activity detector, more on than off. This in turn will decrease the phones double-talk performance, which means you cannot interupt the person talking, as you own voice is attenuated by your own phone as leakage from the downlink.

Acoustic design intent in the handset can also contribute, the speakers chosen, the DSP applied, the passive & active filtering settings also play a part.

The most significant part is the plastics around the speaker. The acoustical design of these reinforce, or attenuate many frequencies, and characterize how precise you need to be with the positioning of the phone.