When sourcing from a factory, you must prioritize IC storage capacity (ROM size), which determines the duration of the sound (typically ranging from 3 to 60 seconds or more). Ensure the sampling rate is at least 8kHz to 12kHz for clear voice playback. Additionally, verify the trigger mechanism options, such as press-button, light-sensor, vibration, or pull-tab, to ensure they align with your toy's design. For high-end applications, look for factories capable of producing OTP (One-Time Programmable) or USB-pluggable chips for custom sound uploads.