field(seewave)
field()所属R语言包：seewave
Near field and far field limits
近场和远场限制
译者：生物统计家园网 机器人LoveR
描述----------Description----------
This function helps in knowing whether you are working in the near or far field.
此功能有助于知道无论你是工作在近场或远场。
用法----------Usage----------
field(f, d)
参数----------Arguments----------
参数：f
frequency (Hz)
频率（Hz）
参数：d
distance from the sound source (m)
的声源的距离（米）
Details
详细信息----------Details----------
Areas very close to the sound source are in the near-field where the contribution of particle velocity to sound energy is greater thant that of sound pressure and where these components are not in phase. Sound propagation properties are also different near or far from the source. It is therefore important to know where the microphone was from the source.<br> To know this, the product k*d is computed according to:
领域非常接近的声源是在近场的贡献的粒子速度的声音的声压和这些组件是不相能量大于吴丹。声音的传播特性也各不相同，或近或远，从源头。因此，重要的是要知道麦克风是从源头上。要知道这<BR>，产品K * d为计算依据：
with d = distance from the source (m), f = frequency (Hz) and c = sound celerity (m/s).<br> If k*d is greatly inferior 1 then the microphone is in the near field.<br> The decision help returned by the function follows the rule:<br>
d =距离从源（米），f =频率（赫兹）和c =声音波速（米/秒）。参考如果k * d是大大下1，那么麦克风是在近场<BR规则>的决定由该函数返回的说明如下：参考
between near and far field limits:
近场和远场之间的限制：
near field:
近场：
.
。
值----------Value----------
A list of two values is returned:
两个值，则返回的列表：
参数：kd
the numeric value k*d used to take a decision
数值K * d曾经作出决定
参数：d
a character string giving the help decision.
一个字符串，决定给予的帮助。
注意----------Note----------
This function works for air-borne sound only.
此功能仅适用于空气传播的声音。
（作者）----------Author(s)----------
Jerome Sueur <a href="mailto:sueur@mnhn.fr">sueur@mnhn.fr</a>
实例----------Examples----------
# 1 kHz near field at 1 cm from the source[1 kHz时的近场源在1厘米]
field(f=1000,d=0.01)
# playing with distance from source and sound frequency[玩距离源和声音频率]
op<-par(bg="lightgrey")
D<-seq(0.01,0.5,by=0.01); nD<-length(D)
F<-seq(100,1000,by=25); nF<-length(F)
a<-matrix(numeric(nD*nF),nrow=nD)
for(i in 1:nF) a[,i]<-field(f=F[i],d=D)$kd
matplot(x=D,y=a,type="l",lty=1,col= spectro.colors(nF),
xlab="Distance from the source (m)", ylab="k*d")
title("Variation of the product k*d with distance and frequency")
text(x=c(0.4,0.15),y=c(0.02,1), c("Near Field","Far Field"),font=2)
legend(x=0.05,y=1.4,c("100 Hz","1000 Hz"),lty=1,
col=c(spectro.colors(nF)[1],spectro.colors(nF)[nF]),bg="grey")
abline(h=0.1)
par(op)
转载请注明:出自 生物统计家园网(http://www.biostatistic.net)。
注：
注1：为了方便大家学习，本文档为生物统计家园网机器人LoveR翻译而成，仅供个人R语言学习参考使用，生物统计家园保留版权。
注2：由于是机器人自动翻译，难免有不准确之处，使用时仔细对照中、英文内容进行反复理解，可以帮助R语言的学习。
注3：如遇到不准确之处，请在本贴的后面进行回帖，我们会逐渐进行修订。
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发表于 2012-9-30 00:13:44
