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The problem states the speed of sound in air is $340 \text{ m/s}$.
We will assume the emitted sound wave has the same frequency as the fundamental frequency of the string, which was calculated in part b) as $f_1 \approx 151.52 \text{ Hz}$.
Given:
Speed of sound in air, $V_{sound} = 340 \text{ m/s}$
Frequency of emitted sound, $f = 151.52 \text{ Hz}$

The relationship between wave speed ($V$), frequency ($f$), and wavelength ($\lambda$) is $V = f\lambda$.
Rearranging for wavelength:

The wavelength of the emitted sound wave is $\boxed{2.243 \text{ m}}$.