A speech signal, band limited to $4 \; \mathrm{kHz}$ and peak voltage varying between $+5 \mathrm{V}$ and $-5 \mathrm{V}$, is sampled at the Nyquist rate. Each sample is quantized and represented by $8$ bits.
If the bits $0$ and $1$ are transmitted using bipolar pulses, the minimum bandwidth required for distortion free transmission is
- $64 \; \mathrm{kHz}$
- $32 \; \mathrm{kHz}$
- $8 \; \mathrm{kHz}$
- $4 \; \mathrm{kHz}$