Here is the same recording, played at 3x speed, this affects the pitch of the recording and makes the sound stand out a lot more. It starts at low volume from the begining of the recording and, at this speed, stops at around 8.5s.Change the display to spectrogram and you can clearly see it...Here is the original recording;http://freesound.org/people/AlienXXX/sounds/348515/#descriptionRecorded from my bedroom at around 9-10pm. The windown was open.Does not sound like a car/motorbike/train/airplane. There is nothing in the room that would make any sound (refrigerator, air-conditioning, fan, etc).I don't know what it is.
神秘的不和諧humming_HP1kHz_x3speed.wav
聲道：2
類型：wav
dissonant、humming、mysterious、night、strange、recording、fast-forward、pitched-up、unknown
不搭調、低唱、神秘、晚、奇怪、記錄、快進、金字了、未知
資料來源：freesound ( https://freesound.org )

Victorian pointing hand traced from http://thegraphicsfairy.com/steampunk-clip-art-images-awesome-hands/
維多利亞時代的指針
finger、hand、pointing、victorian、vintage， manicule
手指、手、指點、維多利亞時代、vintage，修指甲
資料來源：openclipart ( https://openclipart.org/ )

Red device, similar to a firealarm with black button, glass to be broken and description, aiming it to freedom in danger.
自由警報
alarm、Freedom、political
報警、自由、政治
資料來源：openclipart ( https://openclipart.org/ )

Alien creature or insect talking (seems distressed). Made by post processing my voice
CreatureTalk_2.wav
聲道：2
類型：wav
distress、bug、squelch、wet、insect、alien、communicate、sci-fi、pain、death
苦難、竊聽器、嘩啦嘩啦地、濕、昆蟲、外僑、通信、科幻、痛、死亡
資料來源：freesound ( https://freesound.org )

Microphone: SM58DAW Used - Audacity & ReaperObjects Used: Cards, Plastic 1m stick, Metal PanMethodology: Recorded cards flicking against one another, combined this with whoosh sounds from a plastic stick (swinging past the microphone) and use synthetic bass sounds with metal pan hits for impact.
箭頭影響1
聲道：1
類型：wav
Arrow、Bow、Metal、Hit、Archery、Impact
箭頭、弓、金屬、擊中、射箭、碰撞
資料來源：freesound ( https://freesound.org )

Propeller-driven plane take-off at Red Bull Air Race Porto 2017
takeoff2.flac
聲道：2
類型：flac
take-off、plane、airplane、red-bull、propeller
脫掉、平面、飛機、紅牛、螺旋槳
資料來源：freesound ( https://freesound.org )

I made fire in the stove of a herders cabin in the alps preparing supper. Outside the wind howling, two meters of snow. This is a raw recording with Zoom H2n.
201603272023_janbockelson_stove_fire.wav
聲道：2
類型：wav
crackling、burning、fireplace、crackle、fire
劈裡啪啦、燃燒、壁爐、裂紋、火
資料來源：freesound ( https://freesound.org )

The Charm of Oxford with sunset
牛津的魅力與日落
building、oxford、remix、silhouette、skyline、sun、sunset
建造、牛津、混音、輪廓、天際線、孫、日落
資料來源：openclipart ( https://openclipart.org/ )

A simple flat engine start stop button.
發動機啟動停止按鈕
auto、button、car、Car stuff、dashboard、engine、push、start、stop
汽車、按鍵、汽車、汽車的東西、儀表板、發動機、推、開始、停
資料來源：openclipart ( https://openclipart.org/ )

Simplified Bee or Bumblebee drawing.
最小的蜜蜂或大黃蜂
Animal、Bee、Biene、Bumblebee、Hummel、Insect、Insekt、Tier
動物、蜜蜂、蜜蜂、熊蜂、胡默爾、昆蟲、昆蟲、一級
資料來源：openclipart ( https://openclipart.org/ )