Answer:
The fundamental frequency is 159 Hz.
Step-by-step explanation:
Given that,
First frequency = 1113 Hz
Second frequency = 1431 Hz
Third frequency = 1590 Hz
Here, three frequencies are separated from each other by the multiple of 159
We need to calculate the fundamental frequency
![1113+159+159=1431\ Hz](https://img.qammunity.org/2021/formulas/physics/college/hze8b5simldtelivbrabl8fdn3narxgm1g.png)
![1431+159=1590\ Hz](https://img.qammunity.org/2021/formulas/physics/college/g60t6vjrl8mh4nmllb2qi4z2sdn19oonht.png)
As,
![(1113)/(159)=7](https://img.qammunity.org/2021/formulas/physics/college/p6ylt0t0k4un94mfblgqxquhh5uz8a2bcs.png)
1113 Hz is the seventh harmonic of 159.
Hence, The fundamental frequency is 159 Hz.