diff --git a/slab/macos-audio/Sources/ACMacAudio/RoomReceiver.swift b/slab/macos-audio/Sources/ACMacAudio/RoomReceiver.swift
index b0295056c..8b41f4df1 100644
--- a/slab/macos-audio/Sources/ACMacAudio/RoomReceiver.swift
+++ b/slab/macos-audio/Sources/ACMacAudio/RoomReceiver.swift
@@ -128,6 +128,7 @@ public final class ACAudioRoomReceiver: @unchecked Sendable {
     private let store = ACAudioPacketStore()
     private var nonce: UInt32 = 0
     private var didLogAudio = false
+    private var didLogSignal = false
     private var lastTrafficNanos: UInt64 = 0
 
     public init(configuration: Configuration) { self.configuration = configuration }
@@ -232,6 +233,10 @@ public final class ACAudioRoomReceiver: @unchecked Sendable {
                         self.didLogAudio = true
                         self.log("audio locked at \(packet.sampleRate) Hz, \(self.configuration.channel.name), gain \(self.configuration.gain)")
                     }
+                    if !self.didLogSignal, packet.pcm16.contains(where: { $0 > 2 && $0 < 254 }) {
+                        self.didLogSignal = true
+                        self.log("signal present (non-silent audio arriving)")
+                    }
                 default: break
                 }
             }
diff --git a/slab/macos-audio/Sources/ACMacAudio/RoomSender.swift b/slab/macos-audio/Sources/ACMacAudio/RoomSender.swift
index 524fa4198..bfd15bdf1 100644
--- a/slab/macos-audio/Sources/ACMacAudio/RoomSender.swift
+++ b/slab/macos-audio/Sources/ACMacAudio/RoomSender.swift
@@ -30,6 +30,7 @@ public final class ACAudioRoomSender: @unchecked Sendable {
     private var sequence: UInt32 = 0
     private var nextPresentationNanos: UInt64 = 0
     private var lastAudioNanos: UInt64 = 0
+    private var lastMeterNanos: UInt64 = 0
 
     public init(configuration: Configuration = .init()) {
         self.configuration = configuration
@@ -147,6 +148,23 @@ public final class ACAudioRoomSender: @unchecked Sendable {
             return
         }
 
+        // Level meter every ~5 s: "locked but silent" downstream is
+        // indistinguishable from success without knowing what the tap
+        // actually carries.
+        let meterNow = ACHostClock.nowNanos()
+        if meterNow &- lastMeterNanos > 5_000_000_000 {
+            lastMeterNanos = meterNow
+            var peak: Float = 0
+            for channel in 0..<2 {
+                for frame in 0..<Int(output.frameLength) {
+                    let v = abs(channels[channel][frame])
+                    if v > peak { peak = v }
+                }
+            }
+            log(String(format: "tap level peak %.4f (%u frames, %d clients)",
+                       peak, output.frameLength, connectedClients.count))
+        }
+
         let now = ACHostClock.nowNanos()
         if nextPresentationNanos == 0 || now > lastAudioNanos + 250_000_000 {
             session = UInt32.random(in: 1...UInt32.max)