Re: smart fans

[Emanuel Berg <moasenwood@zoho.eu>]

David Christensen wrote:

> These are the equations and conversion factors needed:
>
>     Bel   = log10(power)
>
>     power = 10 ** Bel
>
>     1 Bel = 10 dB
>
> So, your calculation should be:
>
> 2021-08-23 23:42:34 dpchrist@dipsy ~
> $ perl -e '$p=0; $p += 10**($_/10) for @ARGV; print
> 10*log($p)/log(10), "\n"' 14.9 15.9 15.9 14.7 29.0
> 29.696732023509

OK, so then the data is

  5 fans:          23.3 dB
  5 fans and HDD:  30.0 dB

;;; -*- lexical-binding: t -*-
;;;
;;; this file:
;;;   https://dataswamp.org/~incal/emacs-init/audio.el

(defun db (d &rest ds)
  (let ((all (cons d ds))
        (sum 0) )
    (cl-loop for a in all do
             (cl-incf sum (expt 10 (/ a 10.0))) )
    (format "%.1f dB" (* 10 (/ (log sum) (log 10))) )))

;; (db 18.9 14.9 14.7 15.9 15.9)    ; 23.3 dB
;; (db 18.9 14.9 14.7 15.9 15.9 29) ; 30.0 dB

> That said, I would just add the continuous fan noise [...]
> And consider the 29.0 dB HDD vibration separately.

Why?

-- 
underground experts united
https://dataswamp.org/~incal