Speech-caption contrastive learning is a multimodal machine learning technique that aligns spoken audio signals with descriptive natural language texts in a shared embedding space. In this approach, neural networks process speech recordings and textual descriptions concurrently, utilizing an objective function that pulls representations of corresponding speech-text pairs closer together while pushing unrelated pairs further apart. By learning to associate complex acoustic, semantic, and paralinguistic cues with descriptive vocabulary, this method bridges audio representations with natural language decoders, supporting downstream tasks such as automated speech captioning, speech emotion analysis, and cross-modal audio-text retrieval.