AI 每日一课

先由标准差求功率，再计算功率比的分贝值。

from math import log10
signal_power = 0.5
noise_std = 0.5
noise_power = noise_std ** 2
snr_before = 10 * log10(signal_power / noise_power)
print("before:", snr_before)
# 只把噪声标准差减半，目标信号功率保持不变
residual_std = 0.25
snr_after = 10 * log10(signal_power / residual_std ** 2)
print("after:", snr_after, "gain:", snr_after - snr_before)
assert abs(snr_before - 3.0103) < 0.001
assert abs(snr_after - 9.0309) < 0.001
assert abs((snr_after - snr_before) - 6.0206) < 0.001

代码说明与扩展

对零均值噪声，P_noise=σ²。把 σ 乘以 1/2，分母乘以 1/4，信噪比增加 10 log10(4)≈6.02 dB。信号功率固定是这里的比较条件；若算法也损伤语音，就需同时检查信号变化。