  We consider the sound ranging problem, which is to find the position of the
source-point from the moments when the wave-sphere of linearly, with time,
increasing radius reaches the sensor-points, in the infinite-dimensional
separable Euclidean space H, and describe the solving methods, for entire space
and for its unit sphere. In the former case, we give some sufficient conditions
for uniqueness of the solution. We also provide two examples with the sets of
sensors being a basis of H: 1st, when sound ranging problem and so-called dual
problem both have single solutions, and 2nd, when sound ranging problem has two
distinct solutions.
