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嘿，HN。我开发了一个名为 Outside In 的小型 iOS 应用程序（<a href="https://apps.apple.com/us/app/outside-in/id6759529344">https://apps.apple.com/us/app/outside-in/id6759529344</a>）。这个想法很简单：你把一个备用/旧 iPhone 放在外面（门廊、窗台、后院），另一个放在床边。外面的手机捕捉那里发生的一切——蟋蟀、雨声、风声，偶尔还有猫头鹰——并通过你的本地 Wi-Fi 将其流式传输到里面的手机。你把里面的手机面朝下放好，然后伴着这些声音入睡。我开发这个应用程序是因为我和我的伴侣过去常常在晚上开着窗户，以便听到外面的声音，但外面的温度并不总是适合这样做。我想要在睡觉时听到开窗的声音，但又不受天气的影响。一些技术细节：手机通过 Bonjour（NWListener/NWBrowser）互相找到对方，然后通过带有长度前缀帧的普通 TCP 连接流式传输 PCM 音频。48kHz 单声道 Float32。没有服务器，没有互联网。所有内容都保留在本地网络上。有一个语音抑制功能，它使用 Apple 的 SoundAnalysis 框架来检测设备上的人声并将其过滤掉。它运行一个滞后门，大约 55% 的置信度阈值用于关闭，大约 30% 用于重新打开，并有 3 秒的保持时间，这样它就不会出现颤动。增益斜坡是每个缓冲区的指数级，以避免出现咔哒声。它的效果出奇地好。人行道上的对话会被抑制，但你仍然可以听到它们后面的蟋蟀声。里面的手机使用加速度计来检测它何时面朝下且静止（gravity.z > 0.85 + 1.75 秒的静止缓冲），然后淡入音频。拿起它时，音频会淡出。整个交互模型基本上是“放下它，然后忘记它”。没有帐户，没有云，没有分析，没有录音。零外部依赖。所有 Apple 框架。免费，无广告，无应用内购买等。我为自己开发了这个应用程序，并认为其他人可能也需要它。很乐意回答问题（不可避免地，有些人会说“我为什么要听 X 城市的外面声音？” :)

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Hey HN. I built a small iOS app called Outside In (<a href="https://apps.apple.com/us/app/outside-in/id6759529344">https://apps.apple.com/us/app/outside-in/id6759529344</a>).The idea is simple: you put a spare/old iPhone outside (porch, windowsill, backyard) and keep the other one by your bed. The outside phone captures whatever's happening out there — crickets, rain, wind, the occasional owl — and streams it to the inside phone over your local Wi-Fi. You flip the inside phone face-down and fall asleep to it.I built this because my partner and I used to leave a window cracked at night to hear the outside, but the outside temperature isn't always compatible with that. I wanted the sounds sleeping with the window open without the weather.Some technical details:The phones find each other via Bonjour (NWListener/NWBrowser), then stream PCM audio over a plain TCP connection with length-prefixed framing. 48kHz mono Float32. No server, no internet. Everything stays on the local network.There's a speech suppression feature that uses Apple's SoundAnalysis framework to detect human voices on-device and gate them out. It runs a hysteresis gate with ~55% confidence threshold to close and ~30% to reopen, with a 3-second hold time so it doesn't flutter. The gain ramping is exponential per-buffer to avoid clicks. It works surprisingly well. Conversations on the sidewalk get suppressed but you still hear the crickets behind them.The inside phone uses the accelerometer to detect when it's face-down and still (gravity.z > 0.85 + a 1.75s stillness buffer), then fades audio in. Pick it up and it fades out. The whole interaction model is basically "put it down and forget about it."No accounts, no cloud, no analytics, no recording. Zero external dependencies. All Apple frameworks. Free, no ads, no IAP etc. I built it for myself and figured others might want it too.Happy to answer questions (inevitably some folks who would say "why would I want to listen to outside in X city?" :)

Show HN: 外界之声 – 将户外夜间声音实时传输到床边。iOS/免费