Final answer:
The sentence uses a simile, an imagery technique that compares the team's happiness with a cackle of hyenas using the word 'as'. Similes and metaphors are key elements in creating vivid imagery in literature.
Step-by-step explanation:
The effective imagery technique employed in the sentence 'Our team was as happy as a cackle of hyenas when we found out we had landed the account.' is a simile. This can be identified by the use of 'as' to compare the happiness of the team to a cackle of hyenas, which is a direct comparison that appeals to the senses and helps create a vivid image in the reader's mind.
Similes and metaphors are common figurative language devices used to create imagery in literature. A simile explicitly uses 'like' or 'as' in the comparison. In contrast, a metaphor implies the comparison without using 'like' or 'as', thereby stating that one thing is another. These rhetorical devices are essential in writing because they allow the reader to form mental images and connections, thereby enriching the experience of the text.