Yasuhiro Iida

Sound reproducing apparatus

A sound reproducing apparatus is provided formed of an acoustic tube having first and second opposite ends, and having substantially a same inside diameter as that of an external acoustic meatus of the user who is wearing the sound reproducing apparatus. A loudspeaker unit is mounted to the acoustic tube intermediate the first and second ends such that a sound radiating surface thereof is directed to one side of the acoustic tube. The acoustic tube has at its first end an auricular attachment which is received at the external acoustic meatus. A second end is formed as a non-sound-reflecting end. The sound reproducing apparatus may also be adapted to have two loudspeaker units mounted to one or more acoustic tubes, respectively, and two auricular attachment sections may be provided, one for each ear. Left and right channel acoustical signals may be respectively input to the respective first and second loudspeaker units for stereo operation.

Acoustic signal reproducing apparatus

An acoustic signal reproducing apparatus for supplying an acoustic signal to a headphone device, in which position-detecting reference signals from a reference signal source are sensed by a pair of signal sensors provided at two places over a listeners head. The turning angle and the relative distance of the head with respect to the reference signal source are calculated by processing units on the basis of these signal sensors and transmission characteristics with respect to an arbitrarily positioned imaginary sound source are found from the information concerning the relative distance and the turning angle, with the reference signal source as a reference position. Acoustic signals are processed by acoustic signal processing devices on the basis of the transmission characteristics to realize binaural reproduction with respect to the imaginary sound source. A level detection unit detects when the output level of at least one of the signal sensors becomes lower than a reference level and, on the basis of a detection output of the detection unit, the acoustic signals supplied to the headphone device are controlled by a control unit to realize a stable binaural playback operation, and an alarm is supplied to the headphone device in response to the output of the level detection unit.

Soft-Output Decoding of 17 Parity Preserve/Prohibit Repeated Minimum Transition Runlength (PP) Code

We propose a novel trellis decoding technique for soft-output decoding of 17 parity preserve/prohibit repeated minimum transition runlength (PP) code. The trellis of the 17 PP code has 21 states and 79 branches. We applied the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm to the trellis to obtain a soft-input soft-output (SISO) decoder. Using this SISO decoder, we have developed a turbo-coded 17 PP system for optical recording. It is experimentally confirmed that the turbo-coded 17 PP system effectively improves the bit error rate (BER) of high-density optical storage.

Application of Low Density Parity Check Codes to High-Density Optical Disc Storage Using 17PP Code

We are developing a high-density recording method for optical disc storage. To improve the density of optical recording systems and increase the operational margin, we previously optimized the PR17PP trellis by merging the PR(1221) trellis and we achieved a higher recording density in optical disc storage. In this paper, we propose a new high-density low density parity check (LDPC)-coded PR17PP system with PR(12221)-ML. We experimentally confirmed that the system significantly increases the tilt margin of 36.0 GB optical disc with Blu-ray disc parameters.

An optimization method for designing high rate and high performance SCTCM systems with in-line interleavers

We present a method for designing high-rate, high-performance SCTCM (serially concatenated trellis coded modulation) systems with in-line interleavers. Using in-line EXIT charts and ML performance analysis, we develop criteria for choosing constituent codes and optimization methods for selecting the best ones. To illustrate our methods, we show that an optimized SCTCM system with an in-line interleaver for rate r = 5/6 and 64QAM has better performance than other turbo-like TCMs with the same parameters.