The frequency of the nth-harmonic is an integer multiple of the fundamental frequency of the string:
[tex]f_n = n f_1[/tex]
where [tex]f_1[/tex] is the fundamental frequency.
Here, we know the frequency of the 4th harmonic [tex]f_4 = 44 kHz[/tex], therefore we can use it to find the fundamental frequency and the following overtones:
[tex]f_1 = \frac{f_4}{4}= \frac{44 kHz}{4}=11 kHz [/tex]
[tex]f_2 = 2 f_1 = 2 \cdot 11 kHz =22 kHz[/tex]
[tex]f_3 = 3 f_1 = 3 \cdot 11 kHz = 33 kHz[/tex]
Since the hearing range of human ear goes from 20 Hz to 20 kHz, it means that only the first harmonic of 11 kHz will be audible to humans.
