A digital wavetable audio synthesizer is described. The synthesizer can generate up to 32 high-quality audio digital signals or voices, including delay-based effects, at either a 44.1 KHz sample rate or at sample rates compatible with a prior art wavetable synthesizer. The synthesizer includes an address generator which has several modes of addressing wavetable data. The address generator's addressing rate controls the pitch of the synthesizer's output signal. The synthesizer performs a 10-bit interpolation, using the wavetable data addressed by the address generator, to interpolate additional data samples. When the address generator loops through a block of data, the signal path interpolates between the data at the end and start addresses of the block of data to prevent discontinuities in the generated signal. A synthesizer volume generator, which has several modes of controlling the volume, adds envelope, right offset, left offset, and effects volume to the data. The data can be placed in one of sixteen fixed stereo pan positions, or left and right offsets can be programmed to place the data anywhere in the stereo field. The left and right offset values can also be programmed to control the overall volume. Zipper noise is prevented by controlling the volume increment. A synthesizer LFO generator can add LFO variation to: (i) the wavetable data addressing rate, for creating a vibrato effect; and (ii) a voice's volume, for creating a tremolo effect. Generated data to be output from the synthesizer is stored in left and right accumulators. However, when creating delay-based effects, data is stored in one of several effects accumulators. This data is then written to a wavetable. The difference between the wavetable write and read addresses for this data provides a delay for echo and reverb effects. LFO variations added to the read address create chorus and flange effects. The volume of the delay-based effects data can be attenuated to provide volume decay for an echo effect. After the delay-based effects processing, the data can be provided with left and right offset volume components which determine how much of the effect is heard and its stereo position. The data is then stored in the left and right accumulators.

Digital wavetable audio synthesizer with delay-based effects processing

Systems, methods, and apparatus to calibrate sounds fields are disclosed. An example device includes a location sensor receiving location data, a processor triangulating the position of a listener based on the location data, and an audio processing component generating a sound field with audio characteristics based on the position of the listener.

Sound field calibration using listener localization

Embodiments described herein may involve dynamically adjusting the equalization of a playback device based on the environment in which the playback device is operating. One embodiment may involve emitting a first audio signal from a playback device, detecting, by the playback device, a second audio signal, where at least a portion of the second audio signal is a reflection of the first audio signal, in response to the detecting, determining one or more reflection characteristics, where each of the one or more reflection characteristics are based on at least the second audio signal, adjusting an equalization setting of the playback device based on the one or more reflection characteristics, and causing an audio track to play according to the adjusted equalization setting.

Audio settings based on environment

A digital wavetable audio synthesizer with an LFO generator is described. The synthesizer can generate up to 32 high-quality audio digital signals or voices, including delay-based effects. The synthesizer includes an address generator which has several modes of addressing wavetable data. The address generator's addressing rate controls the pitch of the synthesizer's output signal. A synthesizer volume generator, which has several modes of controlling the volume, adds envelope, right offset, left offset, and effects volume to the data. The synthesizer LFO generator can add LFO variation to: (i) the wavetable data addressing rate, for creating a vibrato effect; and (ii) a voice's volume, for creating a tremolo effect. The LFO generator assigns two triangular-wave LFOs to each of the 32 possible voices. One LFO is dedicated to vibrato (frequency modulation) effects and the other to tremolo (amplitude modulation) effects. It is possible to ramp the depth of each LFO into and out of a programmable maximum. The parameters for each LFO are stored in local memory. When creating delay-based effects, data is stored in one of several effects accumulators. This data is then written to a wavetable. The difference between the wavetable write and read addresses for this data provides a delay for echo and reverb effects. LFO variations can be added to the read address to create chorus and flange effects.

Wavetable audio synthesizer with low frequency oscillators for tremolo and vibrato effects

Systems and methods are provided for device playback calibration. An example implementation involves a computing device receiving, via a microphone, detected audio content rendered by at least one playback device. The implementation also involves the computing device modulating the detected audio content with a modulation signal such that the modulation signal has a modulation frequency determined based on an input frequency range of a processing unit. The implementation also involves providing the modulated audio content to the processing unit; and determining, via the processing unit, an equalization setting for the at least one playback device.

Playback device calibration

An audio signal data processing system comprises input device for sequentially supplying an audio signal data, data memory control device for writing the audio signal data into a data memory and reading-out the data from the data memory, delay memory control device for sequentially reading-out the audio signal data from the data memory and storing the data into a location of a delay memory indicated by a writing address and for reading-out the audio signal data from a location of the delay memory indicated by a reading address and writing the data into the data memory, address designating devices for designating the writing and reading addresses, arithmetic device for multiplying a predetermined coefficient data to the audio signal data having been read-out by the delay memory control device and written into the data memory, and output device for providing the audio signal data in accordance with a result of operation by the arithmetic device. The data memory control device and the delay memory control device write and read the audio signal data into and from the data memory through data buses independent from each other.

Norimichi Katsumura

Papers

Audio signal processing system having independent and distinct data buses for concurrently transferring audio signal data to provide acoustic control