US 4,701,956 AGranted

Tone signal processing device

AssigneeNippon Gakki Seizo Kabushiki Kaisha

InventorMitsumi Katoh

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Abstract

A digital filter is provided between a tone signal generation circuit which supplies a digital tone signal in accordance with a first sampling frequency and a sampling circuit which resamples this digital tone signal in accordance with a second sampling frequency which is lower than the first sampling frequency. This digital filter filters the input digital tone signal with such amplitude-frequency characteristics as to be able to substantially remove an aliasing noise produced due to the second sampling frequency (e.g., with low-pass filter characteristics having a cut-off frequency which is 1/2 the second sampling frequency). This removes high frequency components producing an aliasing noise from the digital tone signal before it is applied to the resampling circuit whereby generation of the aliasing noise in resampling is prevented. The resampling is performed for adapting the digital tone signal to an operation clock frequency of an effect imparting circuit provided in a posterior stage for imparting, in digital, a tone effect such as a modulation effect to the digital tone signal.

Claims9

Dependent claims

An improved electronic musical instrument comprising:

clock means for providing a relatively high frequency clock signal having an associated clock period;
tone signal generation means for providing a first digital tone signal having a first sampling frequency four times as high as said clock frequency, corresponding to 64 sample points per cycle of the digital tone signal, and having an associated first sampling period;
a digital filter for receiving said first digital tone signal and filtering out substantially all frequencies above a predetermined cutoff frequency, said digital filter comprising:
first, second and third delay circuits, coupled in series and providing first, second and third delayed digital tone signals, respectively, said first delay circuit receiving said first digital tone signal, each delay circuit having 16 stages each stage delaying said digital tone signal by one first sampling period, each said delay circuit thereby delaying said digital tone signal by 16 first sampling periods;
a selector circuit coupled to said tone signal means, said first, second and third delay circuits and said clock means for selecting at every clock pulse one of said first digital digital tone signal and said first, second and third delayed digital tone signals and providing such selected signal as a selector output signal;
filter coefficient means for providing a predetermined filter coefficient signal every clock period;
and
a multiplier circuit for receiving said selector output signal and said filter coefficient signal and multiplying said two signals every clock period and providing said multiplied signals as a multiplier output signal;
an accumulator circuit for receiving said multiplier output signal and accumulating said multiplier output signal over 64 clock periods and providing an accumulated multiplier output signal every 64 periods;
and
sampling means for receiving said accumulated signal and resampling said signals every 16 first sampling periods.

8 more elements

A tone signal processing device comprising at least clock means for providing a clock signal having a relatively high frequency and associated clock period, tone signal generation means for supplying a digital tone signal having a plurality of channels and having a first sampling period in accordance with a first sampling frequency corresponding to a specified number of sample points per cycle of the digital tone signal, sand sampling means for resampling said digital tone signal in accordance with a second sampling frequency which is lower than said first sampling frequency, the improvement comprising:

at least one delay means, each having a plurality of stages, for receiving said digital tone signal and delaying said signal by a fixed multiple of said clock period at each stage and each delay means providing a delayed digital tone signal;
selector means for receiving said digital tone signal and said at least one delayed digital tone signal and alternately selecting at each said clock period one of said digital tone signal and said at least one delayed digital tone signal and providing said selected digital signal as a selector output signal, wherein each of said digital tone signal and said at least one delayed digital tone signal are selected once during said first sampling period;
digital filter coefficient means for supplying a digital filter coefficient signal at each clock period;
multiplier means for receiving said selector output signal and said digital filter coefficient signal and providing a multiplied digital signal at each said clock period;
and
accumulator means for receiving the multiplied digital signal at each clock period and accumulating said received multiplied digital signals during a predetermined number of clock periods and providing said accumulated signal to said sampling means;
and
wherein said specified number of sample points per cycle corresponds to the ratio of the clock frequency to the second sampling frequency.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/784,860Filed 4 Oct 1985
Priority: JP 59-21151511 Oct 1984
Granted: 20 Oct 1987
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G10H 1/125
By filtering complex waveforms: using a digital filter
G10H 2250/095
Filters for musical processing or musical effects; Filter responses, filter architecture, filter coefficients or control parameters therefor:…
G10H 2250/115
Impulse response, i.e. filters defined or specified by their temporal impulse response features, e.g. for echo or reverberation applications: fIR…
G10H 2250/545
Details of musical waveform synthesis, i.e. audio waveshape processing from individual wavetable samples, independently of their origin or of…