h******2
发帖数: 1498 | 1 the noise most likely comes from the bearings in the pedal. lubricate the
pedal bearings first (WD40, etc) and see if the noise goes away. |
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m******e
发帖数: 428 | 2 crank arms don't usually make noises.
if there are noises when you pedal, it's probably one of two things, pedals
or bottom bracket. |
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O****e
发帖数: 3290 | 3 I suspect my BB has a problem or has been damaged. I am still waiting for
the bracket tool for the overhaul. There is some delay in the shipping.
Anyway, I would like to get some expert's advise before starting the work.
My bike is making this noise (clicking or cricking) for some time. Not so
much on a flat terrain but quite prominent on climbing especially a steep
one. And, it sounds like from the BB/Crank area. But, I was not sure since
bike noise can be quite strange and can originate from o |
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s****y
发帖数: 267 | 5 【 以下文字转载自 Outdoors 讨论区 】
发信人: shmimy (睡在窗台上的猫), 信区: Outdoors
标 题: How to reduce roofrack noise
发信站: BBS 未名空间站 (Wed Aug 5 23:13:44 2009, 美东)
Just install a thule roofrack. Cannt get along with the wind noise. How do
you guys do with it? Is a fairing really useful? Thanks. |
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m********n
发帖数: 2995 | 6 are you saying the roof rack itself makes a huge noise? or with the kayak on
? my experience is that sometimes the tie down strap causes some noise
problem. |
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m******h
发帖数: 5753 | 7 Yes,
that is right, the kayayk/canoe themselves make some noise, but noise
mostly comes from rope or string used to fasten the load, I use thin strings
instead of the the luggage packing strip, that makes a lot better.
on |
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d*********o
发帖数: 6388 | 8 http://bigstory.ap.org/article/mistakes-miscalculations-doom-de
The seeds of Denver's stunning Super Bowl self-destruction were planted
during Wednesday's practice when coach John Fox decided to turn down the
speakers that simulate crowd noise because "it's not an away game."
At the Jets' practice facility Wednesday, Fox had his team run several live
drills with eight speakers on one side of the field blaring crowd noise to
help with concentration, but he didn't turn them on full blast.
"Normall... 阅读全帖 |
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b*******r
发帖数: 6655 | 9 哪位能推荐一个入门级别的? 我对音质并没有什么要求, 只是坐车太吵闹, 想安静一下
而已, 也不欣赏吵闹的音乐, 所以希望不会因为Noise Canceling 增加额外的noise. |
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x****k
发帖数: 661 | 10 最近继续做research，本来计划用来拍银河风景照的，不过看到很多人抱怨long
exposure会有很多Hot pixel noise。如果开Long exposure noise reduction会好些，
原理就是subtract dark frame，但是这样的话时间加倍了。而且如果要连续拍多张叠
加的话也会受影响。
不过大部分帖子是去年的，今年也有，少很多，不知道是firmware update解决一些了
还是大家已然习惯了。。。
不知道大家有什么经验？ |
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m****y
发帖数: 11 | 11 I just bought a Lenovo G570 i3. The hard drive will make some click click
noise every once a while. I disabled any hibernation, sleep or hard disk
turning off. It is better than before. But once in a while, I still hear the
click noise. Anybody have any idea of what causing this clicking? And I am
still trying to figure out how can I type Chinese here. The first time using
windows 7, out of dated :(. |
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i***0
发帖数: 160 | 12 据我理解，background （背景）是除样品外的信号，而noise （噪音）是指信号的稳
定度，即非样品导致的信号强度的小范围震动。signal/noise取决于仪器的敏感度。而
背景往往取决于样品的纯度 |
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m*******l
发帖数: 220 | 13 谢谢各位的回复。我的问题在于white noise幅值小，但数量大，有可能对计算结果产
生较大的影响。
并且在我的原始数据中（来自断电的静止钢结构重型机械），存在高频的信号（１６０
－２００hz），信号的频率是变化的。这是机械上解释不了的。这种情况会不会是white
noise造成的？或者是数据采集设备造成的？ |
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z******i
发帖数: 3 | 14 white noise is randomly distributed, so it won't be any specific frequency.
Your noise must come from somewhere else |
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s*******y
发帖数: 4173 | 15 TRANSISTOR有两种噪声，
热噪声肯定是gm大了比较好，
flicker noise我的理解是和gate面积成反比，
pmos是相对比nmos flicker noise小，但那主要
是因为面积大，可那是牺牲的是频率。当然还是
要看你的应用，对那些频段的噪声比较关注，
corner frequency 想在那。 |
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m*******n
发帖数: 236 | 16 现在手头只有一个noise source,知道ENR,还有一台Vector network analyzer,请问如
何测量noise
figure? |
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r*****e
发帖数: 620 | 17 首先要确定noise来自源信号 还是放大器自身 或者是scope
看了这两张图我觉得noise是测试设备造成的
你用的是coaxial cable么，或者active probe?
如果probe的signal和ground在测试点相距比较远的话可能会引入噪声，或者可以加一
个metal shield box试试看 |
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f**h
发帖数: 1149 | 18 non-gaussian white noise是怎么定义的？对带non-gaussian white noise的信号，什
么估计是最优的？
面试中被问到这种问题，只有乱回答了 |
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h********t
发帖数: 555 | 19 it doesn't matter how you sample the data, the quantization noise is
still not band limited, because quantization will introduce high frequency components.the quantization noise spectrum is not relevant to the sampled data spectrum.
In
fs/
you
2.
quantization |
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f*********t
发帖数: 37 | 20 Well if 'the sampling rate of FFT test is different from the sampling rate
of the data converter under test', then it makes sense to me.
I am not a circuit design or mixed signal guy. At the input of DSP or
digital ASIC, everything are discrete at sampling rate. Acutally sometimes
they are just some data sitting in memory :). I was talking about the
quantization noise at this point. I think this is also the quantization
noise defined in may DSP books like the one wrote by Proakis. I modeled
thos |
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H***F
发帖数: 2501 | 21 The newest verison of HSPICE support tran noise
why....
难道noise对digital circuit一点也不重要吗？。。。 |
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H****E
发帖数: 444 | 22 我看HSPICE主页上也说有transient noise的新特性，但是我查了一遍2009.3的manual
，竟然没有
搜到任何和transient noise相关的内容。。。
高手可有example code或者有没有讲解此功能的链接？谢啦。。。 |
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m*****t
发帖数: 3477 | 23 to simplify my question:
If you plot the output noise current power spectre, the corner frquency is
much higher than that of the equivalent input noise voltage power spectre.
why is that?
amplif
这时 |
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ET
发帖数: 10701 | 24 不是。。你这corner frequency是怎么定义的？
fcorner 是flicker noise density = thermal noise density那点
的frequency ..
所以，理论计算上只能是一个点。 怎么会从10hz to 100khz?
you |
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m*****t
发帖数: 3477 | 25 So you believe when you plot the output noise spectrum, you will get the
frequency dependent part meet the noise floor around KHz?
t |
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ET
发帖数: 10701 | 26 昨晚simulted a 45nm nmosfet using predictive spice model.
attached here. the spectral density also included a 10K resistor's noise
performance tho.
the flicker noise corner frequency is in the range of ~Mhz.. |
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H***F
发帖数: 2501 | 27 input noise fc仿真的和output noise fc不一样啊。你再仿真一下？
65nm: W/L=1u/1u, Fc=3M |
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H***F
发帖数: 2501 | 28 你用cadence工具不？直接选input noise不就行了？
想请教一下，如何仿真input-referred noise呢？以CS amp with R load为例，谢谢。 |
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s*****o
发帖数: 22187 | 29 没有input source noise啊? 如果是同样的电路，你仿真的input referred noise啥样
子呢？ |
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R*****o
发帖数: 204 | 30 一般来讲，input referred flicker noise是怎么随着工艺变化的，比如说0.5um的
和0.13um的transistor，他们的input referred flicker noise和cornor frequency哪
个高哪个低。 |
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s*****o
发帖数: 22187 | 31 在一定频率下，Fmin随ft增大而减小，应该和flicker noise关系不大，用的都是
thermal noise的公式。反正thomas lee这一部分我就从来没看懂过。 |
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ET
发帖数: 10701 | 32 我对rfic知之甚少，你也能用这个机会帮我更新下。
1）现在的cad tool里，对于vco里的phase noise, 能simulate 1/f upconversion con
tribution? 我知道cadence 5.0之前都没这个model.
2) integrated analog ic里，device noise无论用在那里都需要考虑。更别说在adc了
。 |
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r*******r
发帖数: 1014 | 33 (1)cadence spectreRF 在 phase noise 上还是有些人品的.
5.0前没有的原因可能是bell lab的 phase noise 的牛paper前8年才出来。
(2)1/f is still difficult to verify at transient level if you care your time
-domain waveform distortion. if quant-error is small then it's an issue for
adc.
(3)how ot optmize for design it is still unknown; how to model it beyond 40nm is also unknown recently.
con
了。 |
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ET
发帖数: 10701 | 34 bell lab的？
不是stanford的hajimiri (?) (with caltech now) 整出来的close form equation？
我说的1/f upconversion那部分。
(3) optmize for design是啥意思？ 是知道transistor level flicker noise info，
如何用它来设计opamp?
ucb ee240 那方法不介绍的挺好？ 从dynamic range ,output swing, 选ota topology
, 计算noise factor, 最后确定transistor size
time
for
40nm is also unknown recently. |
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c***u
发帖数: 843 | 35 大家能否推荐一些关于noise的书籍或者paper? 有没有关于HEMT里面phase noise的书
？ MOSFET的书也行？
多谢！！ |
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w******3
发帖数: 30 | 36 R2's noise directly being added to output noise. You can then refer to input
by divided the gain of the circuit. |
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C*****y
发帖数: 203 | 37 刚刚做rf没多久，被要求给receiver做个LO signal的divider，说了phase noise的要
求。据说需要看pm的part，或者必须要加一个limiter再看pss的phase noise，还有说
要先算jitter再用公式算的。不过这几个结果都不一样呀，请板上的大牛帮忙看看，给
个指教吧。 |
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b********t
发帖数: 28 | 38 LNA是会放大noise，但它自身引入的white noise小，有利于整个Rx的NF。
在Rx加了LNA之后sensitivity会提高。 |
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l****o
发帖数: 184 | 39 我觉得没有关系，就像你说的 noise average is zero.
但是在一定时间内，noise 对电压还是有影响的。个人理解 |
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m*******n
发帖数: 103 | 40 你的测试结果显示的是哪一种情况的noise floor 高一些？
从理论上看，noise figure在open port 和match的情况，计算结果应该也不同啊？ |
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x***y
发帖数: 830 | 41
我估计是loaded 的时候noise大些，因为有source resistance产生的noise. |
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d****6
发帖数: 971 | 42 我就是概念不清楚
text book上推的时候都是resistor产生的4ktb noise
open的时候就不知道noise是怎么个情况了
难道open理想情况下就没有热噪声了吗 |
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m*******1
发帖数: 13 | 43 No matter you have a short, an open, or a load terminated on the input, the
input noise temperature depends on the physical temperature of the
termination. The difference is that the noise power contributed by the LNA
itself when terminated differntly varies. |
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o****x
发帖数: 287 | 44 哪个方向有noise, 把机器对着那个方向就把noise zap掉了, 呵呵
赶脚理论上应该可以实现呀, 有这方面的专家木有?
讨论讨论哈! |
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w********u
发帖数: 90 | 45 请问各位大神， 白噪声符合泊松分布（from wiki），那么其噪声功率应该是
和其signal 成正比。 那么电流为 I (A) 的白噪声功率应该是 sqrt（I）(A) in rms.
可是书上说 Inoise=sqrt（2*q*I*B）， B:bandwidth ，
怎么理解里面的2*B ? And, also does it mean at infinite bandwidth, noise is
also infinite?
困扰我很久的问题，谢谢! |
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y******g
发帖数: 41 | 46 thanks for the reply.
my understanding is that garch talks aboutthe conditional variance of the
prediction error, which means that the conditional variance is a linear
funtion of past random shocks and past volatility.
My question is: if a time series shows a white noise feature in its ACF, is
it possible that its volatility having a GARCH model?
because even though the ACF shows a white noise feature (close to 0 at all
lags), but the time series plot still shows somewhat clustered volatility. |
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t********a
发帖数: 810 | 47 I cant remember the basic concepts, but I think it could. basically Garch
talks about the clustering of variance, which means non-linear correlation,
while white noise is mostly about linear correlation.
in other words, garch says the second moment of w_t and w_{t-1} are not
orthogonal, while white noise says the first moment of w_t and w_{t-1} are
orthogonal. these might not be contradictory. that's why you see flat acf
for garch at non-zero lags. |
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m***e
发帖数: 4 | 48 有无数种方法，这里面有关于分数布朗运动产生noise的一些文献：
Wei-Xing Zhou and Didier Sornette, Statistical Significance of
Periodicity and Log-Periodicity with Heavy-Tailed Correlated Noise,
Int. J. Mod. Phys. C 13 (2), 137-170 (2002)
看我后面的，呵呵，一个程序 |
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D******a
发帖数: 394 | 49 Car: 2008 Hundai Sonata
Symptom: When I park the car in the down direction of a slope and start the
engine, there is always a grinding noise there, I am not sure it is from
the engine or some belt or pulley close to the engine. No engine light on
and the car runs smooth after that.
Funny thing is when I park the car in the up direction of the slope, there
is no such noise.
Any comments are highly appreciated. Thanks. |
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