Numerizing and describing various sensations are important in the discussion of human information processings as well as in the construction of an information processing system, simulating human recognition and behavior. This paper considers the psychophysical function when the stimulus is multidimensional and the corresponding sensation is one‐dimensional. We define a state space spun by several physical continua and a psychological continuum, which is regarded as an n‐dimensional Riemannian space. the psychophysical function is defined as a certain geometrical invariant in this space. A metric is introduced into this state space based on the threshold of discrimination, and functions are derived which are permissible in this case as psychophysical functions. As an application of this formulation a problem is considered to establish a correspondence between the luminance and the brightness of the colored light. It is shown that when Weber's law and Ekman's law apply to the threshold of discrimination, Stiles' law and Abney's law can be derived as the permissible psychophysical functions.
This paper proposes a method f o r reduci n g a d d i t i v e n o i s e from noisy speech s i g n a l . The e f f e c t i v e n e s s of t h i s comb f i l t e r i n g method i s demonstrated v i a experiments. The method i s a p p l i c a b l e t o n o i s e with varying power and non-flat spectrum. L i s t e n i n g experiments show t h a t t h e proposed method improves the s u b j e c t i v e SIN and t h e sound a r t i cu l a t i o n of extremely noisy speech. t i o n of t h i s method f o r t h e r e d u c t i o n of q u a n t i z a t i o n n o i s e and n o i s e caused by b i t e r r o r i n PCM speech i s i n v e s t i g a t e d . mental r e s u l t s i n d i c a t e t h a t : Applica-Experi-(1) For e r r o r -f r e e 2-to-5 b i t PCM t h e proposed method improves t h e s u b j e c t i v e quali t y of t h e speech equivalent t o one b i t ; (2) For b i t e r r o r r a t e 'ranging from 10-3 t o 10-1, t h e proposed method improves t h e q u a l i t y of 8-bit PCM speech e q u i v a l e n t t o t h e reduction of e r r o r rate down t o about 1 / 3 -1 / 5 . It i s very e f f e c t i v e f o r reducing t h e quantiz a t i o n noise i n 4-bit PCM speech. (3) The proposed method i s p a r t i c u l a r l y u s e f u l f o r improving t h e sound a r t i c u l a t i o n of extremely noisy speech. 1. I n t r o d u c t i o n Speech s i g n a l s i n communication and audio systems u s u a l l y are contaminated by noise. Noise causes degradations i n t h e q u a l i t y of speech s i g n a l s and reduces t h e performances of audio processing equipment. Therefore , r e s e a r c h and development of techniques f o r n o i s e r e d u c t i o n a r e v e r y important. Noise reduction methods proposed previously include Wiener f i l t e r i n g , a d d i t i v e noise c a n c e l i n g [13 , s p e c t r a l s u b t r a c t i o n [2-41 , method based on c o r r e l a t i o n [5] , and speech modeling [ 6 ] . These methods assume t h a t t h e power and spectrum of n o i s e are known v a l u e s . The comb f i l t e r i n g n o i s e red u c t i o n method proposed by t h i s paper does n o t have t o r e l y on such assumptions. Even though comb f i l t e r i n g method h a s been used i n t h e p a s t [ 7-91 , comprehensive q u a n t i t a t i v e e v a l u a t i o n p e r t i n e n t t o p i t c h e x t r a c t i o n of noisy speech and removal of harmonic noise has not been presented. The n o i s e reduction method proposed h e r e u t i l i z e s t h e p i t c h ext r a c t i o n [ l o ] and comb f i l t e r i n g techniques
This paper describes the trial production results for two linearizers, one being a compact, lightweight MIC linearizer developed to improve the input‐output nonlinear characteristics of an earth station HPA and the other being a new soft‐limiter linearizer (SL‐LRZ) followed by an amplitude limiter. The symmetric construction of the MIC linearizer is easily implemented with MIC techniques, operates over a wide frequency band and its nonlinearities can be controlled electrically. Also, the transfer characteristics of a TWTA with SL‐LRZ are such that its amplitude response is linear up to saturation, it maintains constant output level beyond saturation and phase shift is not likely to occur. The TWTA with SL‐LRZ can reduce intermodulation products due to nonlinearities of the TWTA in amplification of multiple carriers and can improve transmission performance when a band‐limited PSK signal is amplified at close to saturation. The test‐fabricated SL‐LRZ is sufficiently small and lightweight for on‐board application.
In general, when a signal with noise is applied to a nonlinear amplifier, the nonlinearity will suppress either the signal or the noise. This property is utilized in this paper; the input signal is applied to nonlinear and linear amplifiers and an output circuit forms their difference. It is found that such a circuit can markedly improve the signal‐to‐noise (S/N) ratio of an input signal containing strong noise. Simple saturation nonlinearity is produced by an element xν(ν < 1); with ν>1 extension‐type nonlinearity characteristics result. A general type of noise is treated as a narrowband noise with a Weibull amplitude distribution. Analysis shows that when the Weibull coefficient is small, the use of the saturation characteristics of a nonlinear amplifier improves the S/N ratio considerably; when the Weibull coefficient is very large, neither extension‐ or saturation‐nonlinearity shows a marked difference. If the signal is contained in narrow‐band noise of constant amplitude, tests confirm the effectiveness of the theory.
The fact that the pulse response of a transistor circuit is accompanied by a phase delay is well known. The quantity β(s), which plays the role of the frequency response of α(s), is expressed in terms of polynomials and the transformation formulas are obtained by introducing a state variable into β(s). After α(s) is set equal to d0e−sm/ωa, this transformation gives a response that agrees satisfactorily with measurement. This is true even when the measured pulse response has a phase delay from the start of response to the steady state conditions. This paper also gives the phase delay element value. When the delay time contained in the element is compared to m/ωα obtained from the response, the delay time of the pulse response can be directly determined within the phase interval from 45° to 90°. In addition, the relationship between the location of centroid of the impulse response coordinate axis and the 50% rise time of the indicial response and the carrier transit time is also investigated.
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