Why did vinyl LP records have quieter surfaces than shellac records?

Vinyl LP records offered quieter surfaces than traditional shellac discs primarily due to the material composition of the records. While shellac records were manufactured using a mixture of natural resin and fillers such as fine clay or other abrasive materials, the introduction of vinyl resins provided a superior, smoother medium for sound reproduction.12

The transition to vinyl in the late 1940s, alongside the development of the long-playing (LP) record, allowed for a significant reduction in surface noise compared to the older 78-rpm shellac discs. The use of these synthetic thermoplastics enabled the creation of microgroove records, which not only improved the signal-to-noise ratio but also allowed for much longer playback times per side.1