為什麼人會有興趣分析『雜訊』呢？因為它幾乎『無所不在』也！且聽聽 JULIUS O. SMITH III 先生說法吧︰
SPECTRAL AUDIO SIGNAL PROCESSING
JULIUS O. SMITH III
Center for Computer Research in Music and Acoustics (CCRMA)
……
An example application of noise spectral analysis is denoising, in which noise is to be removed from some recording. On magnetic tape, for example, “tape hiss” is well modeled mathematically as a noise process. If we know the noise level in each frequency band (its power level), we can construct time-varying band gains to suppress the noise when it is audible. That is, the gain in each band is close to 1 when the music is louder than the noise, and close to 0 when the noise is louder than the music. Since tape hiss is well modeled as stationary (constant in nature over time), we can estimate the noise level during periods of “silence” on the tape.
Another application of noise spectral analysis is spectral modeling synthesis (the subject of §10.4). In this sound modeling technique, sinusoidal peaks are measured and removed from each frame of a short-time Fourier transform (sequence of FFTs over time). The remaining signal energy, whatever it may be, is defined as “noise” and resynthesized using white noise through a filter determined by the upper spectral envelope of the “noise floor”.
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若是我們知道 □ ○ 『雜訊特徵』，或可改善『信噪比』乎？！
Signal-to-noise ratio
Signal-to-noise ratio (abbreviated SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise.
S/N ratio is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise.
While SNR is commonly quoted for electrical signals, it can be applied to any form of signal (such as isotope levels in an ice core or biochemical signaling between cells or financial trading signals).
The signal-to-noise ratio, the bandwidth, and the channel capacity之時矣◎ of a communication channel are connected by the Shannon–Hartley theorem.
Signal-to-noise ratio is sometimes used metaphorically to refer to the ratio of useful information to false or irrelevant data in a conversation or exchange. For example, in online discussion forums and other online communities, off-topic posts and spam are regarded as “noise” that interferes with the “signal” of appropriate discussion.[1]
如果比類那個『白色雜訊』，豈非語音活性檢測
Voice activity detection
Voice activity detection (VAD), also known as speech activity detection or speech detection, is a technique used in speech processing in which the presence or absence of human speech is detected.[1] The main uses of VAD are in speech coding and speech recognition. It can facilitate speech processing, and can also be used to deactivate some processes during non-speech section of an audio session: it can avoid unnecessary coding/transmission of silence packets in Voice over Internet Protocol applications, saving on computation and on network bandwidth.
VAD is an important enabling technology for a variety of speech-based applications. Therefore, various VAD algorithms have been developed that provide varying features and compromises between latency, sensitivity, accuracy and computational cost. Some VAD algorithms also provide further analysis, for example whether the speech is voiced, unvoiced or sustained. Voice activity detection is usually language independent.
It was first investigated for use on time-assignment speech interpolation (TASI) systems.[2]
的『理論閾值』發凡啊！？
然而如何能將『不想要』的訊號，都視之為『雜訊』耶？？
Signal-to-interference-plus-noise ratio
In information theory and telecommunication engineering, the signal-to-interference-plus-noise ratio (SINR[1]) (also known as the signal-to-noise-plus-interference ratio (SNIR)[2]) is a quantity used to give theoretical upper bounds on channel capacity (or the rate of information transfer) in wireless communication systems such as networks. Analogous to the SNR used often in wired communications systems, the SINR is defined as the power of a certain signal of interest divided by the sum of the interference power (from all the other interfering signals) and the power of some background noise. If the power of noise term is zero, then the SINR reduces to the signal-to-interference ratio (SIR). Conversely, zero interference reduces the SINR to the signal-to-noise ratio (SNR), which is used less often when developing mathematical models of wireless networks such as cellular networks.[3]
The complexity and randomness of certain types of wireless networks and signal propagation has motivated the use of stochastic geometry models in order to model the SINR, particularly for cellular or mobile phone networks.[4]
Description
SINR is commonly used in wireless communication as a way to measure the quality of wireless connections. Typically, the energy of a signal fades with distance, which is referred to as a path loss in wireless networks. Conversely, in wired networks the existence of a wired path between the sender or transmitter and the receiver determines the correct reception of data. In a wireless network ones has to take other factors into account (e.g. the background noise, interfering strength of other simultaneous transmission). The concept of SINR attempts to create a representation of this aspect.
Mathematical definition
The definition of SINR is usually defined for a particular receiver (or user). In particular, for a receiver located at some point x in space (usually, on the plane), then its corresponding SINR given by
where P is the power of the incoming signal of interest, I is the interference power of the other (interfering) signals in the network, and N is some noise term, which may be a constant or random. Like other ratios in electronic engineering and related fields, the SINR is often expressed in decibels or dB.
當下『語音科技』正致力超越
牙牙學語
牙牙學語 是兒童發展語言的一個階段，在這段語言習得期間，嬰兒好像要嘗試用嘴巴把聲音說出來，但還未能產生任何可辨別的詞彙。嬰兒在出生後不久開始會牙牙學語期，此時需經過幾個階段像是嬰兒的聲音行為戲目會擴大，他們的發聲就會變得越來越像語言 。[1] 嬰兒通常年齡大約在12個月時會開始產出能辨認的詞彙，但在這段時間後，牙牙學語期可能還會繼續一段時間。 [2] 牙牙學語可以被視為語言發展的先驅或是僅作為聲音實驗。身體構造的發展也涉及到牙牙學語之中，它仍需要在小孩一歲時發展。[3] 這種持續性的身體發育負責一些能力上的改變還有讓嬰兒能產出不同的聲音變化 。異常發展，如某些健康狀況、發育遲緩和聽力障礙可能阻礙小孩正常牙牙學語的的能力。 雖然仍有人反對語言是人類獨有的能力，但牙牙學語並非人類物種所僅有。[4]
之時呦☆