Final answer:
Lower pitched sounds are caused by vibrations with lower frequencies; thus, option 'b' is correct. Frequency determines pitch, and amplitude is related to loudness.
Step-by-step explanation:
Lower pitched sounds (more bass) are caused by vibrations with lower frequencies. This is because the frequency of a sound wave determines its pitch, with lower frequencies corresponding to lower pitches. One characteristic of low-frequency sounds is that they tend to have longer wavelengths than high-frequency sounds, as they both travel at the same speed in a given medium. Additionally, amplitude is related to the loudness or volume of a sound; larger amplitudes result in louder sounds, while smaller amplitudes produce softer sounds. Therefore, the correct answer to the question is 'b. Lower frequencies.'
An example illustrating this concept is the use of different speakers to produce various sounds. A large speaker, known as a woofer, is typically used to emit lower-frequency, bass sounds, whereas a small speaker, called a tweeter, emits higher-frequency sounds.