MySQL beta at CHEARSdotinfo co uk

滤器 种类 and 响应/反应 Curves

The specifications of 為耳/音频 设备 通常 include a figure for 频率 响应/反应 This 术语 is a shorter 形（曲）式 of 幅频 响应/反应

Each 种类 of 滤器 has its own characteristic 频率 响应/反应 曲线 Typical 频率 响应/反应 curves for four 基础 种类 of 滤器 are shown in figure 5 23 低通 高通 带通 and 带阻 or notch

Shelving 滤器 shown in figure 5 24 提升 or cut all 频率 above or below a 特定 阀值 Their names can be confusing because a 高 shelving 滤器 acts like a 低通 滤器 when it is adjusted to cut 高 频率 and a 低 shelving 滤器 acts like a 高通 滤器 when it is adjusted to cut 低 频率

An 重要 property of a 滤器 is its 截止 频率

The steepness of a filter's slope is 通常 specified in 术语 of dB/分贝 of 衰减 or 提升 每（一个） 倍频程（八度） abbreviated dB/octave For 例如 a 6 dB/octave slope on a 低通 滤器 makes a 平滑 衰减 or rolloff while a 90 dB/octave slope makes a sharp 截止 figure 5 26

滤器 Q值 and Gain

Many 带通 滤器 have a 控制 旋钮 either in 软件 or 硬件 for Q值 An intuitive 定义 of Q值 is that it represents the 度 of 共鸣 within a 带通 滤器 When the Q值 is 高 as in the narrowest inner 曲线 the 频率 响应/反应 is sharply focused around a 峰 共鸣 频率

Q值 = Freq center/ Freq highcutoff - Ffreq lowcutoff

Another property of a 带通 or 带阻 滤器 is its 增益 This is the amount of 提升 or cut of a 频率 带/乐队 It shows up as the height or 深 of the 带/乐队 in a 响应/反应 曲线 figure 5 28 When passing a 信号 through a 高 Q值 滤器 care must be taken to ensure that the 增益 at the 共鸣 频率 the height at the 峰 does 不 过载 the 系统 causing 失真 Many 系统 have 增益补偿 电路 in their 滤器 that prevent this kind of 过载