diff --git a/README.md b/README.md
index ae92e66..4bcdd21 100644
--- a/README.md
+++ b/README.md
@@ -124,6 +124,12 @@ python3 web/webui.py --port 8788 --bind 127.0.0.1   # 也可以直接跑
     设备 `node.name` 随之后缀改变 → 配置里记的 `node.target` 失效 → WirePlumber 回落到其它输出
     （实测落到 HDMI，表现为"没声音"或"声音从显示器出来"）。
     本项目的 `空间音频 开` 已带自检：设备名失效时自动重新探测并重建配置。
+12. **★★ 虚拟声卡的音量不会被保留**（2026-09-13，爆音反复的根因）：
+    filter-chain 每次重建（重载 PipeWire、开机、切设备）都是**全新的节点**，
+    没有历史音量 → 回到默认 **1.0** → 整链直接削波。
+    用户看到的现象是"我明明调低了，怎么又炸了"——**而且调低的那一刻音量可能刚被重置**。
+    **修法两处**：① `capture.props` 里写 `node.volume = 0.25`（重建时的默认值）
+    ② 切换命令每次补写一遍（兜底）。
 13. **判定设备是否存在不能用 `pw-cli info`**：它对不存在的名字也返回成功。要用 `pw-dump`
     按 `node.name` 精确比对。
 
diff --git a/web/index.html b/web/index.html
index 93e1dab..8cf9987 100644
--- a/web/index.html
+++ b/web/index.html
@@ -31,6 +31,10 @@ button.primary:hover{background:#1e4028}
 button.fix{background:#3a2418;border-color:#5c3a26}
 button.fix:hover{background:#4a2e1e}
 #msg{margin-top:12px;font-size:13px;min-height:20px;color:var(--warn)}
+#lv{width:100%;height:120px;display:block;border:1px solid var(--bd);
+    border-radius:6px;background:#121212}
+.lvn{display:flex;gap:18px;margin-top:8px;font-size:12px;flex-wrap:wrap}
+.lvn b{font-variant-numeric:tabular-nums;font-weight:600}
 .nums{display:flex;align-items:center;gap:10px;margin-top:6px}
 #volval{font-variant-numeric:tabular-nums;min-width:52px;text-align:right;color:var(--ok)}
 input[type=range]{flex:1;accent-color:#4ade80;height:4px}
@@ -60,6 +64,15 @@ input[type=range]{flex:1;accent-color:#4ade80;height:4px}
   想更响请改 IR 增益（见 README）。</div>
 </div>
 
+<div class="card"><h2>电平（物理输出）</h2>
+  <canvas id="lv"></canvas>
+  <div class="lvn">
+    <span class="k">峰值 <b id="pk" class="v">-</b></span>
+    <span class="k">RMS <b id="rm" class="v">-</b></span>
+    <span class="k">余量 <b id="hd" class="v">-</b></span>
+  </div>
+</div>
+
 <div id="msg"></div>
 
 <script>
@@ -129,10 +142,86 @@ async function doFix() {
   setTimeout(refresh, 5000);
 }
 
+const cv = document.getElementById('lv');
+const cx = cv.getContext('2d');
+const DB_LO = -60, DB_HI = 6;
+
+function dbY(db, h) {
+  const t = Math.max(0, Math.min(1, (db - DB_LO) / (DB_HI - DB_LO)));
+  return h - t * h;
+}
+
+// Catmull-Rom 插值转三次贝塞尔 —— 得到平滑曲线(而不是折线)
+function smooth(pts) {
+  if (pts.length < 2) return '';
+  let d = 'M ' + pts[0].x + ' ' + pts[0].y;
+  for (let i = 0; i < pts.length - 1; i++) {
+    const p0 = pts[i - 1] || pts[i], p1 = pts[i];
+    const p2 = pts[i + 1], p3 = pts[i + 2] || p2;
+    d += ' C ' + (p1.x + (p2.x - p0.x) / 6) + ' ' + (p1.y + (p2.y - p0.y) / 6) +
+         ', ' + (p2.x - (p3.x - p1.x) / 6) + ' ' + (p2.y - (p3.y - p1.y) / 6) +
+         ', ' + p2.x + ' ' + p2.y;
+  }
+  return d;
+}
+
+function drawLevel(pts) {
+  const w = cv.width = cv.clientWidth * 2;
+  const h = cv.height = 240;
+  cx.setTransform(1, 0, 0, 1, 0, 0);
+  cx.clearRect(0, 0, w, h);
+  cx.font = '18px system-ui';
+  [-60, -48, -24, -12, -6, -3].forEach(function (db) {
+    const y = dbY(db, h);
+    cx.strokeStyle = '#242424'; cx.lineWidth = 1;
+    cx.beginPath(); cx.moveTo(0, y); cx.lineTo(w, y); cx.stroke();
+    cx.fillStyle = '#4a4a4a';
+    cx.fillText(db + ' dB', 8, y - 5);
+  });
+  cx.strokeStyle = '#7f1d1d'; cx.lineWidth = 2;     // 0dBFS 削波线
+  cx.beginPath(); cx.moveTo(0, dbY(0, h)); cx.lineTo(w, dbY(0, h)); cx.stroke();
+  if (!pts.length) return;
+  const n = pts.length;
+  const X = function (i) { return n === 1 ? w : i * w / (n - 1); };
+  function line(key, color, lw) {
+    const P = pts.map(function (p, i) { return { x: X(i), y: dbY(p[key], h) }; });
+    cx.strokeStyle = color; cx.lineWidth = lw;
+    cx.lineJoin = 'round'; cx.lineCap = 'round';
+    cx.stroke(new Path2D(smooth(P)));
+    return P;
+  }
+  const rp = line('rms', '#4ade80', 4);
+  line('peak', '#fbbf24', 2);
+  const last = rp[rp.length - 1];
+  cx.fillStyle = '#4ade80';
+  cx.beginPath(); cx.arc(last.x, last.y, 5, 0, Math.PI * 2); cx.fill();
+  if (pts[n - 1].peak > -0.1) {                     // 削波整体闪红
+    cx.fillStyle = 'rgba(248,113,113,0.22)';
+    cx.fillRect(0, 0, w, h);
+  }
+}
+
+async function level() {
+  const d = await api('/api/level');
+  const pts = (d && d.points) || [];
+  if (pts.length) {
+    const p = pts[pts.length - 1];
+    document.getElementById('pk').textContent = p.peak.toFixed(1) + ' dBFS';
+    document.getElementById('rm').textContent = p.rms.toFixed(1) + ' dBFS';
+    const hd = -p.peak;
+    const el = document.getElementById('hd');
+    el.textContent = hd.toFixed(1) + ' dB';
+    el.className = 'v ' + (hd < 3 ? 'bad' : hd < 6 ? 'warn' : 'ok');
+  }
+  drawLevel(pts);
+}
+
 async function refresh() { render(await api('/api/status')); }
 
 refresh();
 setInterval(refresh, 5000);
+setInterval(level, 150);
+level();
 </script>
 </body>
 </html>
diff --git a/web/webui.py b/web/webui.py
index ed8b565..f4d1214 100644
--- a/web/webui.py
+++ b/web/webui.py
@@ -4,11 +4,16 @@
 from __future__ import annotations
 
 import argparse
+import array
 import json
+import math
 import os
 import re
 import subprocess
 import sys
+import threading
+import time
+from collections import deque
 from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
 from urllib.parse import parse_qs, urlparse
 
@@ -19,6 +24,67 @@ CONF = os.path.expanduser("~/.config/pipewire/pipewire.conf.d/90-cinema-spatial.
 SINK_51 = "cinema_spatial_sink"
 SINK_UP = "cinema_spatial_up_sink"
 
+# 电平表: 从物理输出的 monitor 取样(耳机真正在放的信号), 每 100ms 一个点。
+# 指标是 dBFS —— 0dBFS 为数字满刻度, 余量 = -peak(dB)。
+# 注意: 96k 重采样/多路叠加会产生 intersample peak, 峰值超过 0 也算削波。
+LEVEL: deque[dict] = deque(maxlen=240)
+LEVEL_LOCK = threading.Lock()
+CHUNK_MS = 100
+
+
+def monitor_name() -> str:
+    """当前物理输出设备的 monitor 源(录到的就是耳机在放的东西)。"""
+    p = phys_sink()
+    return p + ".monitor" if p else ""
+
+
+def _level_worker() -> None:
+    """持续录物理输出, 按 CHUNK_MS 切块算 RMS/Peak(dBFS)。"""
+    rate = 48000
+    per = rate * CHUNK_MS // 1000 * 4          # f32 每样本 4 字节
+    while True:
+        mon = monitor_name()
+        if not mon:
+            time.sleep(2)
+            continue
+        proc = None
+        try:
+            proc = subprocess.Popen(
+                ["pw-record", "--target", mon, "--rate", str(rate),
+                 "--channels", "1", "--format", "f32", "-"],
+                stdout=subprocess.PIPE, stderr=subprocess.DEVNULL, env=_env())
+            while True:
+                raw = proc.stdout.read(per) if proc.stdout else b""
+                if not raw or len(raw) < per:
+                    break
+                a = array.array("f")
+                a.frombytes(raw)
+                pk = max(abs(v) for v in a)
+                rms = math.sqrt(sum(v * v for v in a) / len(a))
+                with LEVEL_LOCK:
+                    LEVEL.append({
+                        "peak": round(20 * math.log10(pk), 2) if pk > 1e-9 else -120.0,
+                        "rms": round(20 * math.log10(rms), 2) if rms > 1e-9 else -120.0,
+                    })
+        except Exception:
+            pass
+        finally:
+            if proc is not None:
+                try:
+                    proc.kill()
+                except Exception:
+                    pass
+        time.sleep(0.5)
+
+
+def start_level_worker() -> None:
+    threading.Thread(target=_level_worker, daemon=True).start()
+
+
+def level_points() -> list[dict]:
+    with LEVEL_LOCK:
+        return list(LEVEL)
+
 
 def _env() -> dict[str, str]:
     e = dict(os.environ)
@@ -118,7 +184,8 @@ def status() -> dict:
     devs = [n for n in nodes("Audio/Sink") if "cinema_spatial" not in n["name"]]
     dv = next((round(vol(d["id"]), 3) for d in devs if d["name"] == t), None)
     return {
-        "default": ds,
+        "default": next((n["desc"] for n in nodes("Audio/Sink") if n["name"] == ds), ds),
+        "default_name": ds,
         "default_is_virtual": "cinema_spatial" in ds,
         "sinks": ss,
         "clock": clock_rate(),
@@ -199,6 +266,8 @@ class Handler(BaseHTTPRequestHandler):
                 self._send(404, b"index.html not found", "text/plain; charset=utf-8")
         elif u.path == "/api/status":
             self._json(status())
+        elif u.path == "/api/level":
+            self._json({"points": level_points(), "monitor": monitor_name()})
         else:
             self._json({"error": "not found"}, 404)
 
@@ -237,6 +306,7 @@ def main() -> int:
     ap.add_argument("--port", type=int, default=8788)
     ap.add_argument("--bind", default="127.0.0.1")
     a = ap.parse_args()
+    start_level_worker()
     srv = ThreadingHTTPServer((a.bind, a.port), Handler)
     print("电影院空间音频控制台: http://%s:%d/  (Ctrl-C 退出)" % (a.bind, a.port))
     sys.stdout.flush()
diff --git a/生成配置.py b/生成配置.py
index e8228af..ec0e1ae 100644
--- a/生成配置.py
+++ b/生成配置.py
@@ -77,6 +77,12 @@ def default_sink_name() -> str:
 _TARGET = os.environ.get("CINEMA_SPATIAL_TARGET") or default_sink_name()
 TARGET_PROP = f'node.target = "{_TARGET}"  ' if _TARGET else ""
 
+# 虚拟声卡的音量。★ 必须写进配置, 否则重建后不保留:
+# filter-chain 重建时新节点没有历史音量, 会回到 1.0 → 整链直接削波爆音。
+# 0.25 ≈ -12dB, 给电影那种高峰值因子瞬态留足余量(见 README 第 10、11 条)。
+VOLUME = os.environ.get("CINEMA_SPATIAL_VOLUME", "0.25")
+VOL_PROP = f"node.volume = {VOLUME}  " if VOLUME else ""
+
 
 def hrir_block(indent: str) -> list[str]:
     """12 个卷积器 + 6 个分发 + 左右耳混音。输入端口: cp<dir>:In"""
@@ -115,7 +121,7 @@ def sink_51() -> list[str]:
     L += ["        ]",
           '        inputs  = [ "cpFL:In" "cpFR:In" "cpFC:In" "cpLFE:In" "cpBL:In" "cpBR:In" ]',
           '        outputs = [ "mixL:Out" "mixR:Out" ]', "      }",
-          "      capture.props  = { node.name = cinema_spatial_sink  media.class = Audio/Sink  "
+          f"      capture.props  = {{ {VOL_PROP}node.name = cinema_spatial_sink  media.class = Audio/Sink  "
           "audio.channels = 6  audio.position = [ FL FR FC LFE BL BR ] }",
           f'      playback.props = {{ node.name = cinema_spatial_out  {TARGET_PROP}'
           "audio.channels = 2  audio.position = [ FL FR ] }",
@@ -165,7 +171,7 @@ def sink_upmix() -> list[str]:
     L += ["        ]",
           '        inputs  = [ "copyFL:In" "copyFR:In" ]',
           '        outputs = [ "mixL:Out" "mixR:Out" ]', "      }",
-          "      capture.props  = { node.name = cinema_spatial_up_sink  media.class = Audio/Sink  "
+          f"      capture.props  = {{ {VOL_PROP}node.name = cinema_spatial_up_sink  media.class = Audio/Sink  "
           "audio.channels = 2  audio.position = [ FL FR ] }",
           f'      playback.props = {{ node.name = cinema_spatial_up_out  {TARGET_PROP}'
           "audio.channels = 2  audio.position = [ FL FR ] }",
diff --git a/空间音频 b/空间音频
index 4f7c67b..8bc7bf8 100755
--- a/空间音频
+++ b/空间音频
@@ -67,6 +67,17 @@ sys.exit(1)
 ' "$t"
 }
 
+# 目标失效 -> 重新探测并重建配置
+# 虚拟声卡音量。★ filter-chain 每次重建后音量都会丢(新节点没有历史音量, 回到 1.0
+# → 整链削波爆音), 所以每次"开"都补写一次。改默认: export CINEMA_SPATIAL_VOLUME=0.3
+apply_volume() {
+  local vol="${CINEMA_SPATIAL_VOLUME:-0.25}"
+  for id in $(wpctl status 2>/dev/null | sed -n '/Filters:/,/Streams:/p' \
+              | grep -oE '[0-9]+\. cinema_spatial[a-z_]*_sink' | grep -oE '^[0-9]+'); do
+    wpctl set-volume "$id" "$vol" >/dev/null 2>&1
+  done
+}
+
 # 目标失效 -> 重新探测并重建配置
 rebuild_if_stale() {
   target_alive && return 0
@@ -96,6 +107,7 @@ if [ -n "$VNAME" ]; then
   cur=$(cur_id)
   [ -n "$cur" ] && echo "$cur" > "$STATE"
   wpctl set-default "$v"
+  apply_volume
   # 耳机自身的音量若被压过, 这里不动它(用户自己的选择)
   echo "已切到「电影院空间音频 ($LABEL)」(id $v)"
   echo "  开之前是「$(nick "${cur:-0}")」"