it is common sense. if scholars mentioned such a measure (adhan of one masjid reaching a place) say 500 years ago, it is common sense that they did not account for loud speakers and modern noises - humming of machines, fans, airconditioners, rumbling buses and screeching cars which can drown a human voice. if not, how else can you calculate a distance of "three-day journey" in miles/kms? one can go round the world in two days (even if you go west to east and account for lost hours).
with a loud speaker or other broadcast systems it can reach other countries. that would mean you can have only one masjid in a country. the correct measure would be: assuming that there are no modern* ambient noises and a man with a powerful voice calls out the adhaan, the distance it reaches. ben franklin attempted to calculate the size of the audience by an experiment in which whitefield was speaking from the steps of some well known building. franklin backed off until he could hear whitefield. and then by allowing 2x2 ft for every person, extrapolated a size of 30,000 people in the audience. baxton boren has an interesting research paper on "maximum intelligible range of the human voice": https://marl.smusic.nyu.edu/papers/boren_dissertation_nyu.pdf though boren attempts to find the theoretical limit and mentions that franklin's experiment disregards other factors such as hearing levels of individuals, which are not the same for everyone etc. but for our case, ben franklin's experiment is good enough with whatever ambient noises were present at that time. the paper is quite interesting, but the point relevant to our discussion is on page 56: the analysis in Chapter IV has suggested that Franklin would have had to have been within about 1.5 m from Front Street to be able to hear significant masking noise from a source in that street. This allows a better estimate of the maximum intelligible distance of about 121m along the ground. on page 62, the simulation puts it at 128m The overall Z-weighted pressure attenuation along Market Street was tested in the computer model by placing virtual receivers along the center of the street, beginning at 4 m from Whitefield’s position, and doubling the distance until 128m, just beyond Franklin’s position. ==== on p45 is the map of the street in question. there are hand drawn pictures of the courthouse on p57, p58 and diagram on p60 (to give you a sense of distance). on p.83 a similar calculation concerning whitefield's audience at moorfields in london. or p.88 kennington common/ kennington park [whitefield reportedly preached at moorfields in the mornings and kennington in the evening] ----- another sound-distance study: http://astheworldtilts.com/index.php/project/a-very-scientific-sound--distance-study/ according to guinness book of world records, the farthest distance human voice can travel is normally 180m in still air. though extreme cases have been observed: http://www.guinnessworldrecords.com/world-records/farthest-distance-travelled-by-a-human-voice *cars and humming machines for example. our ears are now used to this din.
Is there any ruling for opening a new masjid near to where an existing Sunni masjid is? Is it anything to do with if the adhan from first masjid can be heard then within that radius there shouldn't be another masjid?
