A wire of density $8 \times 10 ^ { 3 } \mathrm {~kg} \mathrm {~m} ^ { - 3 }$ is stretched between two clamps 0.5 m apart. The extension developed in the wire is $3.2 \times 10 ^ { - 4 } \mathrm {~m}$. If $Y = 8 \times 10 ^ { 10 } \mathrm {~N} \mathrm {~m} ^ { - 2 }$, the fundamental frequency of vibration in the wire will be $\_\_\_\_$ Hz