An audio tone \$Acos(\omega t + \theta)\$ undergoes uniform quantization by a quantizer that has the average quantization noise power \$q^2/6\$ joules, where \$q\$ is the quantization step size. If the dynamic range of the quantizier is adjusted to 15dB and the signal-to-quantization-noise ratio (SQNR) is targeted to be at least 40dB, how many bits per sample are needed to code each sample?
This is an past-exam exercise from my university. I tried to solve it, but I only got a solution as a function of \$A\$. Anyone can give me a hint? I don't know what I'm missing. Thanks!