Final answer:
The property that is greater for the second, louder sound wave produced by the flute is amplitude, while the frequency, speed in air, and wavelength of the sound wave remain the same.
Step-by-step explanation:
When a person produces two sound waves using a flute where the second sound wave is louder than the first despite having the same pitch, the property that is greater for the second sound wave is amplitude. The amplitude of a sound wave corresponds to its loudness or volume. A higher amplitude indicates a louder sound. Since the pitch, which is determined by the frequency of the wave, remains the same for both sound waves, it is not the frequency that has increased. The speed in air of sound is not affected by the loudness of the sound and remains constant for a given medium under the same conditions. The wavelength also remains the same because it is tied to the frequency, which has not changed.