Acoustic shocks have been previously documented in high-amplitude jet noise, including both the near and far fields of military jet aircraft. However, previous investigations into the nature and formation of shocks have historically concentrated on stationary, ground run-up measurements, and previous attempts to connect full-scale ground run-up and flyover measurements have omitted the effect o...

This clinical trial was undertaken to evaluate the subjective benefit obtained from hearing aids employing automatic switching second-order adaptive directional microphone technology, used in conjunction with digital noise reduction, as compared to a fixed directional microphone or omnidirectional microphone response with the same digital noise reduction. Data were collected for 49 participants...

We present a novel hardware device that combines a regular microphone with a bone-conductive microphone. The device looks like a regular headset and it can be plugged into any machine with a USB port. The bone-conductive microphone has an interesting property: it is insensitive to ambient noise and captures the low frequency portion of the speech signals. Thanks to the signals from the bonecond...

This thesis describes the design of a low-power speech detector chip. It will be used between an electret microphone and a microcontroller and will generate a digital wake-up signal for the microcontroller when the audio signal is sufficiently “speechlike” to initiate higher-level processing of the amplified audio signal. The rest of the time, the microcontroller will sleep and consume nearly n...

An acoustic testing approach based on the concept of a microphone sensor surrounding the product under test is proposed. Partial microphone signals are processed simultaneously by a test system computer, according to the objective of the test. The spatial and frequency domain selectivity features of this method are examined. Sound-spatial visualization algorithm is observed. A test system desig...

In this paper we present SRI’s results on the 1993 ARPA CSR Spoke Evaluations. This evaluation used the same HMM acoustic models as those used in SRI’s hub system: gender-dependent Genonic HMM’s. The system was made robust by modifying the front end algorithms to estimate the cepstral features (the HMM models were not modified). The robust front-end used a wide bandwidth (100-6400Hz) and estima...

Using the difference in the spatial domain (direction or location) between a target signal and noise, a system with a microphone array can achieve the goal of noise reduction and speech enhancement in various environments, especially, in speech-like noisy environments. This paper deals with various issues related to the use of microphone arrays in hearing aids. It includes overall principles, a...

In certain communication environments, digital speech transmission systems must work in severe acoustic environments where the noise levels exceeds 110 dB. In other environments, speakers must use an oxygen face mask. In both situations, the intelligibility of encoded speech falls below an acceptable level. We have developed a technique for improving speech quality in these situations. Previous...

Paper deals with acoustic source localization using microphone array using time-delay estimation method. It describes main requirements, hardware design of the microphone units with automatic gain control preamplifiers with integrated anti-aliasing filters and finally its connection to standard personal computer equipped with Advantech PCI1716 multifunction data acquisition card. Next part of t...

In this paper, we present the use of stethoscope and silicon NAM microphones in automatic speech recognition. NAM microphones are special acoustic sensors, which are attached behind the talker’s ear and can capture not only normal (audible) speech, but also very quietly uttered speech (non-audible murmur). As a result, NAM microphones can be applied in automatic speech recognition systems when ...