Which instrument sounds one octave lower than its standard version?

The double bass is the instrument that sounds one octave lower than its standard orchestral version. This characteristic is due to its construction and the length of its strings, which vibrate at a lower frequency compared to higher-pitched instruments. The double bass is the largest string instrument in the orchestra, and its design allows it to produce deep, resonant tones that are one octave lower than the cello.

In contrast, the piccolo and flute are both higher-pitched instruments, with the piccolo sounding an octave higher than the flute. The celeste, a percussion instrument, is known for its bright, bell-like timbre and also does not operate within the same pitch range as the double bass. Therefore, in this context, the double bass correctly represents an instrument that sounds an octave lower, making it the appropriate choice.