This question might be more scientific than historical so I'll give a short answer from a scientific perspective.

Since I can't find a measurement of the sound level of a galloping horse with an armoured hussar on top, I'll take a dB of 80 at a distance of 8 m to be a reasonable guess (according to this link a motorcycle at that distance is 90 dB and a car is 70 dB).

Sound intensity drops off as 1/r^2, so at 1 km, the sound intensity is reduced by a factor of about 16,000.

Luckily this is about the number of horses in your example, so the 18,000 horses at 1 km has about the same sound intensity as one horse at 8 m.

At about 10 km, the sound intensity is dropped by another factor of 100, corresponding to -20 dB, so 60 dB in total, which according to the above link corresponds to the noise level of an office or conversations in a restaurant. Or, according to the numbers above the sound of 18,000 horses at 10 km has the same intensity as the sound of one horse as 80 m.

This means that the wind would have been a major factor. If it blew the sound away from the Ottomans they should not have been able to hear 18,000 hussars galloping at 10 km, but at 1 km they should unless the wind was very strong.

Grund shaking is a little more tricky. It is unaffected by wind of course, but the intensity may not fall off a 1/r^2, since some sound waves (in the ground) stays at the surface and would fall off only as 1/r. So maybe it could be possible to feel the ground shaking from a cavalry charge further away than you can hear it, but probably only if the wind was towards the charge.

I'm guessing that the hussars only actually galloped the final short distance and held something like a trot at even closer than 1 km, so maybe bring the 80 dB above down to 60 dB if you want the effect of trotting horses, which brings the sound intensity at 10 km down to 'library' level according to the link...