The Raman spectra of single-wall carbon nanotubes produced by a laser and are process were studied between 5 and 500 K. The linewidth versus temperature dependence of the low-frequency Raman bands between 150 and 200 cm(-1) deviates from that expected for phonon decay through a phonon-phonon scattering mechanism. The experimental results and their analysis provide convincing evidence that each of the low-frequency Raman bands is a superposition of several narrower Raman lines corresponding to tubes of nearly the same diameter. At low temperatures the width Delta(T) = gamma + Gamma(T) of these components is determined mainly by the temperature-independent part gamma approximate to 2 cm(-1).