Time frequency-based methods have been employed for event detection in audio signals. The spectrogram can be used to extract loudness and energy functions by taking the row sum. The loudness function has been differentiated to obtain the on-set events of the audio. The same could be replicated in case of bio-signals such as phonocardiograms to extract on-set and off-set boundaries. Continuous Wavelet Transform based Time-Frequency algorithm for on-set and off-set Event-detection has been developed for Phonocardiograms and the same has been tested on the PCG dataset hosted in Physionet repository. To validate the simulation, real implementation has also been carried out with real heart sound recordings obtained from Bluetooth based stethoscope called the stemoscope. The simulation carried out using PCG sounds from the Physionet database gave an F1-score of 99.11%. Similar results were found using the real heart sound recordings from stemoscope with an F1- score of 99.30%. Experimental evaluation and Simulations both indicate that Continuous Wavelet Transform based time frequency algorithm can be used to derive on-set and off-set events of the sounds in the PCG signal.