A two-temperature model of optical excitation of acoustic pulses in conductors has been developed. According to this model, the energy of light at first is absorbed by free carriers and only then is the optical pulse energy transferred to long-wavelength phonons of the conductor lattice. It is shown that the shape of the acoustic pulse excited by a laser in conductors can be presented as a convolution of the laser pulse envelope and the transfer function. An analytical dependence of the transfer function on time is derived.