Singing Live Sound Card (Professional Condenser Microphone)

Frequency Response: A range of 20Hz to 20kHz is ideal for capturing the full spectrum of the human voice. 
Sensitivity: This indicates how much output you get for a given sound pressure level. Values around -34dB (or even -45dB) with a 0dB=1V/Pa reference are common. 
Signal-to-Noise Ratio (SNR): A higher SNR (e.g., 78 dB) results in a cleaner, less noisy recording or output. 
Polar Pattern: For live vocals, a uni-directional or cardioid pattern is excellent, as it picks up sound primarily from the front while rejecting sounds from the sides and rear. 
SPL (Sound Pressure Level): A maximum SPL of 132 dB or higher is necessary to handle loud vocals without distortion.