  Selection rules of ultrasound attenuation and sound velocity renormalization
are analyzed in view of their potential application to identify Pomeranchuk
instabilities (electronic nematic phase). It is shown that the transverse sound
attenuation along [110] direction is enhanced by the Fermi surface fluctuations
near a d_{x2-y2}-wave Pomeranchuk instability, while the attenuation along
[100] direction remains unaffected. Moreover the fluctuation regime above the
instability is analyzed by means of a self-consistent renormalization scheme.
The results could be applied directly to Sr3Ru2O7 which is a potential
candidate for a Pomeranchuk instability at its metamagnetic transition in
strong magnetic fields.
