Try pairing a microphone with your favorite IoT platform. The problem with this approach is that, initially, you would have to find a way to calibrate it.
Another option would be the Grove (Arduino).
As for the "outdoor-ness" of a sensor, just shield it from the weather and other disrupting elements.
There is a product called IoTSENS Sound and Noise Sensor. As the specification say, it has following features.
Identify areas of high sound intensity of 30-100 dB
Low maintenance costs
Improved sound environment management
Indoor and outdoor application
Direct connection to SIGFOX and LoRa communications
Another one is TA120, which ...
You can trigger Record and Play from pins described in  and printed in board. Audio signal can be saved to .wav with ALSA library  and saved to SD card. Then it can be sent as HTTP POST to server.
One issue is that ISD1820 is meant for looping, so you have to manually stop recording when time is 20sec.
They do already exist, though they're not easy to find. Here's a bluetooth one on ebay for instance. Obviously, however, in order to remotely use that one, you would have to have it constantly paired with a computer that is nearby and connected to the internet.
However, there are also wifi enabled digital sound meters, such as the Noise Sentry RT-W.
Requirements: Multiple rooms, spotify, airplay mini-jack.
Functionalities: Activating speakers on presence/motion. Playing Spotify when you get home.
This is actually a very broad question that can have a very broad set of answers. However, let me explain how I would do this.
For up to about 4 rooms, you could use an amplifier that has different "...
This isn't a single box with 4 outputs as requested, but we use 2 Sonos CONNECTS that are each a source for our whole home system. Both CONNECTS stream Apple Music, Spotify, Pandora, and a ton of other music/radio services. So, in your case, a single CONNECT consolidates the online sources, but you need a CONNECT device per audio input to your pre-amp.
A two-way switch needs a simple on-off signal, a four way switch needs two on-off signals at a minimum (of course, you could also use 4 on-off switches for 4 wires, and that would allow two switches to be on at once. You could even link the switching to work so that any powered device is on. This switching (and the analogue aspect) all happens at the far end,...
Zigbee can work on analog signals. I have interfaced an LDR sensor to one zigbee and sent the data wirelessly to other zigbee which is connected to the arduino uno. On, uno i received the LDR sensor data and was able to implement it to do according to my project. I'll say you should start there. Integrating audio signals on the other hand require more ...
For an easy start I would go with PIR (Passive InfraRed) sensors to detect presence. They are quite nice and cheap. On detection, you should activate your room sound system, this might be done in several ways.
Maybe a BT loudspeaker and its power supply controlled by the PIR sensor. Well, this idea is a bit rough about the edges, but it could be worth a try....
You can create multi speaker groups with Google Assistant devices (Google Home, Google Nest mini, Google Nest Hub...) and you can "cast" the audio to these groups directly from your phone.
The app you use to play the audio needs to support casting, but nearly all do since the actual support is provided by the Google Play Services library and it's just a ...
May be a bit biased here, since I've worked with this technology a fair amount and enjoyed it, but I'd go with a Raspberry Pi, personally probably the Raspberry Pi 3.
The board will cost ~$30, plus a microSD (unless you opt for a network boot which would save you that cost).
Audio input will be possible through USB. Bluetooth, WiFi, and ethernet are all ...
I looked around for an answer, and while it seems unlikely that you will get an authoritative answer without doing the experiment yourself, there is this reddit thread which indicates that the music is only streamed to one of the devices (the master), which then streams to the other devices.
It is debated whether a device will always take the stream from the ...
Sorry, this is too long for a comment, and there is the beginning of an answer in it, especially if I get more info from the OP.
Can you define "cheap"? Sub $5? $10? $120? $50?
And, what does "Arduino input" mean? Pin comparability? Code comparability? sing he Arduino IDE?
For instance, ESP32 comes with BT & WiFI out of the box, and is certainly ...