Noise reduction method and apparatus utilizing filtering of a dithered signal
AssigneeSony Corporation
InventorsAyataka Nishio, Tohru Sugihara
Life of this patent
Estimating the term…
Abstract
A noise reducing method and apparatus for reducing quantization error or noise generated on quantizing input signals, such as digital audio signals, wherein a dither signal concentrated in signal energy in the low frequency range is summed to the input signal and the resulting sum signal is sent to a quantizer. The quantizer error generated in the quantizer is fed back via a noise filter to the input side of the quantizer. The resulting signal has a smoothed noise floor and has noise components suppressed in a frequency range to which the human hearing mechanism exhibits high sensitivity, thus realizing the sound quality comparable to that of the input signal which prevailed prior to noise shaping.
Claims4
A noise reducing apparatus comprising:
- quantization means for quantizing a signal fed thereto;
- subtraction means for subtracting the signal fed to said quantization means from an output signal of said quantization means;
- first filter means for filtering a signal output from the subtraction means;
- dither signal generating means for generating a dither signal having flat frequency characteristics;
- a second filter for continuously low-pass filtering a low frequency signal to which human hearing is sensitive from said dither signal to generate a low-pass filtered signal;
- and
- addition means for summing the low-pass filtered signal from the second filter with the signal output from the first filter and for providing a summed signal to the quantization means.
A noise reducing apparatus for recording a noise-reduced signal on a recording medium, comprising:
- quantization means for quantizing a signal fed thereto;
- subtraction means for subtracting the signal fed to said quantization means from an output signal of said quantization means;
- a first filter for filtering a signal output from the subtraction means;
- dither signal generating means for generating a dither signal having flat frequency characteristics;
- a second filter for continuously low-pass filtering a low frequency signal to which human hearing is sensitive from said dither signal to generate a low-pass filtered signal;
- addition means for summing the low-pass filtered signal from the second filter with the signal output from the first filter and for providing a summed signal to the quantization means;
- and
- means for recording the noise reduced signal from the quantization means on the recording medium.
Dependencies are inferred from the claim text.