diff --git a/src/components/MicrophoneLevelMeter.stories.tsx b/src/components/MicrophoneLevelMeter.stories.tsx
index 19aaa34dc..933fa1866 100644
--- a/src/components/MicrophoneLevelMeter.stories.tsx
+++ b/src/components/MicrophoneLevelMeter.stories.tsx
@@ -42,18 +42,18 @@ type Story = StoryObj<typeof meta>;
 
 /** A quiet room: hiss below the noise floor lights nothing. */
 export const Silent: Story = {
-  args: { state: { type: "level", level: constant(0) } },
+  args: { state: { type: "level", level$: constant(0) } },
   play: async ({ canvasElement }) => {
     await expect(litSegments(canvasElement)).toBe(0);
   },
 };
 
 export const QuietSpeech: Story = {
-  args: { state: { type: "level", level: constant(5) } },
+  args: { state: { type: "level", level$: constant(5) } },
 };
 
 export const NormalSpeech: Story = {
-  args: { state: { type: "level", level: constant(12) } },
+  args: { state: { type: "level", level$: constant(12) } },
   play: async ({ canvasElement }) => {
     // A floor, not a count: the count follows from the design's bar and gap sizes.
     await expect(
@@ -63,18 +63,18 @@ export const NormalSpeech: Story = {
 };
 
 export const LoudSpeech: Story = {
-  args: { state: { type: "level", level: constant(LEVEL_SCALE) } },
+  args: { state: { type: "level", level$: constant(LEVEL_SCALE) } },
 };
 
 /** The three volumes differ in how many bars are lit, not only in colour. */
 export const VolumesAreDistinguishable: Story = {
-  args: { state: { type: "level", level: constant(5) } },
+  args: { state: { type: "level", level$: constant(5) } },
   play: async ({ canvasElement, mount }) => {
     const lit: number[] = [];
     for (const level of [5, 12, LEVEL_SCALE]) {
       await mount(
         <MicrophoneLevelMeter
-          state={{ type: "level", level: constant(level) }}
+          state={{ type: "level", level$: constant(level) }}
         />,
       );
       lit.push(litSegments(canvasElement));
@@ -121,7 +121,7 @@ export const NoDevice: Story = {
 
 /** The same meter at two widths: the bars keep their size and only their count changes. */
 export const ShapeStaysTheSameAtAnyWidth: Story = {
-  args: { state: { type: "level", level: constant(12) } },
+  args: { state: { type: "level", level$: constant(12) } },
   play: async ({ mount, args }) => {
     const narrow = await measureAt(mount, args, 180);
     const wide = await measureAt(mount, args, 400);
diff --git a/src/components/MicrophoneLevelMeter.test.tsx b/src/components/MicrophoneLevelMeter.test.tsx
index 3e4960540..171f208c1 100644
--- a/src/components/MicrophoneLevelMeter.test.tsx
+++ b/src/components/MicrophoneLevelMeter.test.tsx
@@ -15,7 +15,7 @@ import { constant } from "../state/Behavior";
 describe("MicrophoneLevelMeter", () => {
   test("announces the level rather than relying on hue", () => {
     render(
-      <MicrophoneLevelMeter state={{ type: "level", level: constant(6) }} />,
+      <MicrophoneLevelMeter state={{ type: "level", level$: constant(6) }} />,
     );
 
     const meter = screen.getByRole("meter", { name: "Microphone level" });
diff --git a/src/components/MicrophoneLevelMeter.tsx b/src/components/MicrophoneLevelMeter.tsx
index fc274a34c..6b21491a4 100644
--- a/src/components/MicrophoneLevelMeter.tsx
+++ b/src/components/MicrophoneLevelMeter.tsx
@@ -88,7 +88,7 @@ export const MicrophoneLevelMeter: FC<MicrophoneLevelMeterProps> = ({
   useLayoutEffect(() => {
     const element = segments.current;
     if (state.type !== "level" || element === null) return;
-    const subscription = state.level.subscribe((level) => {
+    const subscription = state.level$.subscribe((level) => {
       element.setAttribute("aria-valuenow", String(level));
       element.setAttribute(
         "aria-valuetext",
@@ -121,9 +121,9 @@ export const MicrophoneLevelMeter: FC<MicrophoneLevelMeterProps> = ({
           aria-valuemin={0}
           aria-valuemax={LEVEL_SCALE}
           // The first paint's value; the effect above keeps it current.
-          aria-valuenow={state.level.value}
+          aria-valuenow={state.level$.value}
           aria-valuetext={t("microphone_level.value", {
-            level: state.level.value,
+            level: state.level$.value,
             max: LEVEL_SCALE,
           })}
         >
diff --git a/src/components/useMicrophoneLevel.test.tsx b/src/components/useMicrophoneLevel.test.tsx
index cef896a78..47b33b996 100644
--- a/src/components/useMicrophoneLevel.test.tsx
+++ b/src/components/useMicrophoneLevel.test.tsx
@@ -36,6 +36,6 @@ describe("useMicrophoneLevel", () => {
 
     // No level carried over from the previous device.
     const state = result.current;
-    expect(state.type === "level" ? state.level.value : state.type).toBe(0);
+    expect(state.type === "level" ? state.level$.value : state.type).toBe(0);
   });
 });
diff --git a/src/components/useMicrophoneLevel.ts b/src/components/useMicrophoneLevel.ts
index b2c17e012..a787a23d5 100644
--- a/src/components/useMicrophoneLevel.ts
+++ b/src/components/useMicrophoneLevel.ts
@@ -13,7 +13,7 @@ import {
 } from "../state/MicrophoneLevel";
 import { constant } from "../state/Behavior";
 
-const IDLE: MicrophoneState = { type: "level", level: constant(0) };
+const IDLE: MicrophoneState = { type: "level", level$: constant(0) };
 
 /** The live level of a microphone, captured only while `active`. */
 export function useMicrophoneLevel(
diff --git a/src/state/MicrophoneLevel.test.ts b/src/state/MicrophoneLevel.test.ts
index 69d7c8a7b..e8f684845 100644
--- a/src/state/MicrophoneLevel.test.ts
+++ b/src/state/MicrophoneLevel.test.ts
@@ -161,7 +161,7 @@ describe("observeMicrophoneState$", () => {
     let levels = 0;
     const subscription = observeMicrophoneState$("mic1").subscribe((state) => {
       states.push(state.type);
-      if (state.type === "level") state.level.subscribe(() => levels++);
+      if (state.type === "level") state.level$.subscribe(() => levels++);
     });
     capture.grant();
     await vi.waitFor(() => expect(levels).toBe(1));
diff --git a/src/state/MicrophoneLevel.ts b/src/state/MicrophoneLevel.ts
index 70f61790b..390f2b3f8 100644
--- a/src/state/MicrophoneLevel.ts
+++ b/src/state/MicrophoneLevel.ts
@@ -67,7 +67,7 @@ export function observeMicrophoneState$(
       let previousFrame = performance.now();
       const current = new BehaviorSubject(0);
       level = current;
-      subscriber.next({ type: "level", level: current });
+      subscriber.next({ type: "level", level$: current });
 
       const read = (): void => {
         analyser.getByteTimeDomainData(samples);