(b)Why do some vibrating systems produce pleasant sounds while others produce harsh(刺耳的) or discordant(不和谐) sounds? When several frequencies are heard simultaneously a pleasant sensation results if the frequencies are in the ratio of small whole numbers(整数), such as32 or5:4.When several frequencies are heard simultaneously, a pleasant sensation results if the frequencies are in the ratio of small whole numbers(整数), such as 3:2 or 5:4. (b) Why do some vibrating systems produce pleasant sounds while others produce harsh (刺耳的) or discordant (不和谐) sounds?