Shot noise in diffusive conductors: A quantitative analysis of   electron-phonon interaction effects
  Using the 'drift-diffusion-Langevin' equation, we have quantitatively analyzed the effects of electron energy relaxation via their interaction with phonons, generally in presence of electron-electron interaction, on shot noise in diffusive conductors. We have found that the noise power $ S_I(\omega )$ (both at low and high observation frequencies $\omega $) drops to half of its 'mesoscopic' value only at $\beta \gtrsim 100,$ where $\beta $ is the ratio of the sample length $L$ to the energy relaxation length $l_{% {\rm ph}}$ (the latter may be much larger then the dephasing length). It means in particular that at low temperatures the shot noise may be substantial even when $L\sim 10^{-2}$ -- $10^{-1}$ cm, and the conductor is 'macroscopic' in any other respect. 
Y. Naveh, D. V. Averin, and K. K. Likharev