* Phonetically: "Heard" is a two-syllable word, with the stress on the first syllable. So, it's longer than a single-syllable word like "cat".
* Duration: The actual duration of the sound "heard" will depend on the speaker and the context. It could be spoken quickly or slowly, making it a longer or shorter sound.
* Perception: Whether "heard" sounds short or long is also subjective. Someone might perceive it as short if they are used to hearing longer words.
Therefore, it's not definitively "short" or "long" without more information.