## Call makers hear tapping noise whilst i hear nothing, same noise when I record on phone

I have Oukitel K5000, Android 7 android phone.

It had been working and at some point months ago, callers started hearing taping noise.

I just restored it to factory settings but still when I go to recorder… when I record something and hear it back… I hear consistent tapping noise.

What else can I do to fix this ?

## Showing that additive Gaussian noise never increases sparsity

Let $$\mathbf{1}\in\mathbb{R}^d$$ be the $$d$$-dimensional all-ones vector and let $$n\sim\mathcal{N}(0, \sigma^2 I_{d\times d})$$, show that $$\frac{\| \mathbf{1} + n \|_1}{\|\mathbf{1} + n \|_2} \ge c \sqrt{d}$$ with high probability in $$d$$, for constant $$c$$ (independent of $$\sigma, d$$).

That is, prove that adding Gaussian noise never significantly improves sparsity in the sense of $$\ell_1 / \ell_2$$ ratio. Generalization to arbitrary dense vectors are of course welcome.

## The mean value of phase noise as a stochastic process

1. What is the mean value of phase noise as a stochastic process?
2. Where can I get a theoretical analysis of this topic?

PS: PLL produces cos(2*πfct+φ(t)). The phase noise refers to φ(t). The mean value of the phase noise what I say refers to the mathematic expectation of phase noise stochastic process φ(t), namely E{ φ(t) }.

## How to Formalize Noise Protocol Messages

I try to understand the messages of the Noise Protocol Framework. The handshakes are based on Diffie-Hellmann key exchange. This is an example for a handshake pattern:

-> e <- e, ee, s, es 

I try to formalize the handshake with mathematical descriptions. For example the mathematical description of the first message is: . Where is a generator and is the private ephemeral key of the sender. But I don’t understand how the values ee and es are calculated. How can these patterns be descriebed mathematically?

## A noise on external screen with MacBook

I have MacBook Pro 13″ 2018. This is Intel Core i5 (2.3 GHz) with Intel Iris Plus Graphics 655 (1536 Mb). MacOs Mojave 10.14.4 is installed. Embedded screen resolution is 2560×1600. I have an Apple’s adapter Thunderbolt 3 -> HDMI as well. What I am doing is connecting Mac to an external display: Dell S2419NH (1920×1080) with HDMI. Mac detects it correctly.

The problem is if I have a close look at the external monitor I see some kind of noise. Like if the white noise was blended with the original picture. This is no problem with colors and if I watch the monitor as usually I do not see any defects. However, after a working day, my eyes are exhausted.

What I have tried:

1. Replaced HDMI cable with the one I use for my 4K TV at home. No result.
2. Replaced the monitor with a different FHD. No result.
3. Replaced adapter with Xiaomi’s one. No result.
4. Tried a home 4K TV (around 45″). Well, I can not claim that the noise is present. I think my eyes may lie at this point.
5. Closely looked at Mac’s display. No noise at all, I suppose. If you ask me where is the noise on Mac, on 4K TV or both, I would say it is likely 4K TV that has it. Nevertheless, my eyes are OK after a day on Mac’s display.
6. Called Apple’s support. The told that monitor is probably Retina incompatible. So, shouldn’t I use FHD displays?

What can cause such an issue? How to get rid of it?

## Cracking/static noise related to fan on MacBook Pro 2017

My MacBook Pro with Touch Bar (13-inch, 2017) makes strange cracking / static interference noise from the left side. First I thought it is the speaker, but it is is independent of the volume level and persists when headphones are plugged in. On the other hand, it appears only when the fans spin (as seen with iStatistica). I also note that the left fan spins always ~100prm slower than the right one.

(I reset SMC and Pram, and run the apple diagnostic with found nothing.)

The computer is ~1.5 years old.

## How do I control excessive fan noise on a Dell XPS Desktop?

System is stock Dell XPS 8700 (2015) with Intel Core i7 4790, Radeon HD R9 270.

Whenever a graphic intensive game is played, the fans inside start spinning up very loudly, sounding like a hair dryer. Also, the fan speed is not constant, it is going up and down continually.

I have tried adjusting the power options cooling settings but nothing helps.

Is there a third party tool that can lock down the fan speed instead of letting it vary wildly?

## Strange problems with MBP (flickering Safari, popping noise, accent menue)

I already asked for help today in another case: MacBook Pro 2018 Battery not correctly working

I don’t know if this problem does relate to my new problem so I’m writing a new post.

My MacBook Pro from December 2018 has a strange problem: Sometimes when I’m searching things via Safari it suddenly shows (while entering the search words) the accent menue. Then it starts making a popping noise which does not stop. When I hover over the apple symbol to shut down the Mac the entries of the menue flicker. I can shut down the Mac and then everything seems to act normally but eventually it starts again. I reseted the SMC and by now it’s acting normal.

Do you have any idea what could be the case with my MacBook? I have already searched in the internet but I could not find anything. What could I do?