For thousands of years, temples have played a significant role in our history, than have anything else in the history of any country. Very often, we hear people criticize the various customs and rituals of ancient-India. But, with a little investigation into the origin of most of these practices, what we dismissed to be cheap superstitions, reveal, yet again, the high intellect of our ancestors. Temples are no exception to this.
Not many of us would have cared to bother about the significance of the vastly abundant bells in our temples. Are they mere invocations to God or are they something more? Physics answers this question. The sound produced by the striking of bells, decays in an exponential manner; to speak in a layman's language, this sound keeps decreasing (in amplitude) at rates that diminish with time. Theoretically, the sound exists for infinite duration, very feebly, though.
The main purpose of the bells has been to facilitate meditation. A person who wishes to meditate (that used to be the motive behind a person's visit to the temple) simply has to bong the bell and tune to it, concentrating on its chime. This chime, steadily diminishing in amplitude, is capable of absorbing a person into deep meditation. The more intensely the person concentrates, the longer will he be able to keep track of this diminishing sound. This fact is very easy to verify, individually. Moreover, it is not difficult to deduce that these bells were traditionally designed to generate sound waves within a particular frequency-band, researched to be the most suitable for meditation.
This purpose, unfortunately, stands defeated in most crowded-temples, where, the striking of the bell by one devotee is immediately followed by that of another, giving the former hardly any time to meditate on it.
Acknowledgement: I would like to thank Dr. Gururaj S. Punekar of NITK for throwing light on these otherwise veiled facts.