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noise

clicks

• transient

• high frequency

• resulting from

  • analog

    • equipment malfunction

  • digital

    • different sampling rates

    • inconsistent clock sources

pops

• transient

• low frequency

• vocal plosives

  • not something heard from a singer

  • a microphone close to a vocalist’s mouth

  • responding to a burst of air

hum and buzz

• hum: primarily just lower harmonics

• buzz: more prominent higher harmonics

• improperly grounded analog circuits and signal chains

• frequency of electrical alternating current (AC) power sources: 50 Hz or 60 Hz

• dynamic range compression➔makeup gain➔raise noise floor➔more noticeable hum and buzz

extraneous acoustic sounds

• airborne

• structure-borne

distortion

hard clipping (overload)

• square wave

• odd numbered harmonics

soft clipping (overdrive)

• creative expression

• gradual transition instead of an abrupt change

• popular and rock music

quantization error

• number of bits of data stored per sample

• applying dither or noise shaping to randomizes the error

perceptual encoder

• lossless

• lossy

• exercises

  • comparing linear PCM to encoded audio

  • subtraction: reverse the polarity of the encoded/decoded to subtract from the original

  • listening to encoded audio through mid-side processing

Technical Ear Trainer: distortion

注意！每次練習時間請勿過長，建議操作五分鐘即休息五分鐘，連續總計不超過一小時。經常性分散練習效果遠勝於短期性密集練習。聽覺疲乏後若仍持續練習，並無法進步，甚至恐有反效果。

audio sample

• sine wave：較不適合練習 bit depth。

• pink noise：較不適合本次練習。

• sound file：請下載本課程第二週介紹之 ITU-R BS.1387 所附音訊檔案，並手動正規化（normalized），再比較同樣參數對不同樣本產生的效果。

distortion type

• soft clipping

• hard clipping

• bit depth

practice types

• matching：配對模式，可練習聆聽每個選項的組合，並切換回題目聲音樣本比對異同。

• matching memory：記憶配對模式，題目只能聽一次，訓練記憶準確度。

• absolute identification：鑑定模式，無法聽到作答參數的聲音輸出。

錄音評析

Beethoven 第七號交響曲第二樂章

MedleyDB

a dataset of multitrack audio for music research

• sample version download

  • LizNelson_Rainfall: vocal

  • Phoenix_ScotchMorris: instrumental

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