The strings are tuned a fifth apart which in equal temparament gives frequencies G3(196 Hz), D4(293.7 Hz), A4, E5(659.3 Hz) using the A4 = 440Hz standard frequencies.
2.Snare drum
The two membranes of the snare drum are acoustically coupled to each other, particularly at the low frequencies. This coupling via the enclosed air acts to double the modes. The lower frequency member of the mode pair involves both heads moving in the same direction and for the higher mode they move oppositely.
1 1 1