Abstract: Combustion engines is main type of noise radiated from diesel engines, so that methods can be devised to reduce the noise levels. Fourier tranformation methods along with block attenuation curves have been used to study the correlation between cylinder pressure and noise radiated from engines. In this research, wavelet method has been used to study noise emitted from a dual injection diesel engine. The results show high variation in cylinder pressure levels and noise emitted which indicate non stationary nature of combustion process.