Steps to reproduce:

1) Download attached project and open in Unity
2) Connect device to machine and pair with bluetooth speaker
3) Build and Run "SampleScene" scene on a device

Note: No sound using bluetooth speaker

Expected result: There should be the sound using bletooth speakers
Actual result: No sound using bluetooth speakers connected to device

Reproduced with:
2017.3.2f1, 2017.4.8f1, 2018.1.9f1, 2018.2.1f1, 2018.3.0a6

Devices under testing:
Reproduced:
VLNQA00099 Google Pixel XL, OS:9, CPU:arm64-v8a, GPU:Adreno (TM) 530
VLNQA00101 Samsung Galaxy Note 8, OS:8.0.0, CPU:arm64-v8a, GPU:Adreno (TM) 540
VLNQA00003 Razer Phone*, OS:7.1.1, CPU:arm64-v8a, GPU:Adreno (TM) 540

Not reproduced with:
VLNQA00128 Samsung Galaxy Note 8, OS:8.0.0, CPU:arm64-v8a, GPU:Mali-G71
VLNQA00139 Vivo Vivo Xplay6*, OS:7.1.1, CPU:arm64-v8a, GPU:Adreno (TM) 530
VLNQA00005 Verizon SM G930V*, OS:7.0, CPU:arm64-v8a, GPU:Adreno (TM) 530
VLNQA00024 Xiaomi MI 5*, OS:7.0, CPU:arm64-v8a, GPU:Adreno (TM) 530
VLNQA00087 Sony SGP511*, OS:6.0.1, CPU:armeabi-v7a, GPU:Adreno (TM) 330
VLNQA00036 Motorola XT1032*, OS:5.1, CPU:armeabi-v7a, GPU:Adreno (TM) 305
VLNQA00030 Lge LG D802 (G2)*, OS:4.4.2, CPU:armeabi-v7a, GPU:Adreno (TM) 330

Note: Using headphones connected with cable worked fine
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Fixed in:
2018.3.0a10