i be a heavy sleeper and work 2 job so every alarm clock i have buy i couldnt hear ... they either chirp or the alarm be very soft and i couldnt hear they to wake for work . so i be always try not to sleep to heavily when i do get to sleep which eventually start make I pretty miserable from lack of sleep ... until i find this alarm clock the sonic boom now i can fall asleep and this clock wake I right up its loud and the vibrate help alot as well . very good product !!!!! very good investment !!!!!